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	$93.36	5.203%	$98.2175	$98.22	$98.20	$98.20
Purchase #2	$240.51	6.268%	$255.5852	$255.59	$255.60	$255.60
Purchase #3	$40.26	4.639%	$42.1277	$42.13	$42.15	$42.10
Purchase #4	$56.69	5.370%	$59.7343	$59.73	$59.75	$59.70
Purchase #5	$101.77	7.634%	$109.5391	$109.54	$109.55	$109.50
Purchase #6	$184.50	9.438%	$201.9131	$201.91	$201.90	$201.90
Purchase #7	$221.72	10.751%	$245.5571	$245.56	$245.55	$245.60
7 purchase totals =	$938.81		$1,012.6740	$1,012.68	$1,012.70	$1,012.60