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	$221.39	10.131%	$243.819	$243.82	$243.80	$243.80
Purchase #2	$221.36	3.460%	$229.0191	$229.02	$229.00	$229.00
Purchase #3	$50.41	9.800%	$55.3502	$55.35	$55.35	$55.40
Purchase #4	$96.57	9.169%	$105.4245	$105.42	$105.40	$105.40
Purchase #5	$124.73	11.681%	$139.2997	$139.30	$139.30	$139.30
Purchase #6	$164.61	12.671%	$185.4677	$185.47	$185.45	$185.50
Purchase #7	$84.91	13.378%	$96.2693	$96.27	$96.25	$96.30
7 purchase totals =	$963.98		$1,054.6495	$1,054.65	$1,054.55	$1,054.70