Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.29	11.324%	$166.1956	$166.20	$166.20	$166.20
Purchase #2	$140.83	4.712%	$147.4659	$147.47	$147.45	$147.50
Purchase #3	$93.86	11.108%	$104.286	$104.29	$104.30	$104.30
Purchase #4	$113.95	11.872%	$127.4781	$127.48	$127.50	$127.50
Purchase #5	$235.47	12.782%	$265.5678	$265.57	$265.55	$265.60
Purchase #6	$174.51	4.191%	$181.8237	$181.82	$181.80	$181.80
Purchase #7	$200.49	6.295%	$213.1108	$213.11	$213.10	$213.10
7 purchase totals =	$1,108.40		$1,205.9279	$1,205.94	$1,205.90	$1,206.00