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	$54.54	10.233%	$60.1211	$60.12	$60.10	$60.10
Purchase #2	$44.39	3.231%	$45.8242	$45.82	$45.80	$45.80
Purchase #3	$234.58	12.655%	$264.2661	$264.27	$264.25	$264.30
Purchase #4	$181.67	3.403%	$187.8522	$187.85	$187.85	$187.90
Purchase #5	$119.89	5.112%	$126.0188	$126.02	$126.00	$126.00
Purchase #6	$220.46	5.862%	$233.3834	$233.38	$233.40	$233.40
Purchase #7	$202.65	13.229%	$229.4586	$229.46	$229.45	$229.50
7 purchase totals =	$1,058.18		$1,146.9244	$1,146.92	$1,146.85	$1,147.00