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	$204.30	8.318%	$221.2937	$221.29	$221.30	$221.30
Purchase #2	$75.59	3.411%	$78.1684	$78.17	$78.15	$78.20
Purchase #3	$147.70	4.571%	$154.4514	$154.45	$154.45	$154.50
Purchase #4	$53.62	13.551%	$60.886	$60.89	$60.90	$60.90
Purchase #5	$221.44	6.178%	$235.1206	$235.12	$235.10	$235.10
Purchase #6	$179.31	9.443%	$196.2422	$196.24	$196.25	$196.20
Purchase #7	$91.40	7.620%	$98.3647	$98.36	$98.35	$98.40
7 purchase totals =	$973.36		$1,044.5270	$1,044.52	$1,044.50	$1,044.60