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	$119.66	6.818%	$127.8184	$127.82	$127.80	$127.80
Purchase #2	$181.33	8.150%	$196.1084	$196.11	$196.10	$196.10
Purchase #3	$88.50	3.650%	$91.7303	$91.73	$91.75	$91.70
Purchase #4	$245.66	5.393%	$258.9084	$258.91	$258.90	$258.90
Purchase #5	$223.85	12.231%	$251.2291	$251.23	$251.25	$251.20
Purchase #6	$105.82	8.149%	$114.4433	$114.44	$114.45	$114.40
Purchase #7	$82.44	7.632%	$88.7318	$88.73	$88.75	$88.70
7 purchase totals =	$1,047.26		$1,128.9697	$1,128.97	$1,129.00	$1,128.80