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	$98.43	13.373%	$111.593	$111.59	$111.60	$111.60
Purchase #2	$112.83	12.462%	$126.8909	$126.89	$126.90	$126.90
Purchase #3	$174.73	11.317%	$194.5042	$194.50	$194.50	$194.50
Purchase #4	$221.72	11.550%	$247.3287	$247.33	$247.35	$247.30
Purchase #5	$7.45	12.658%	$8.393	$8.39	$8.40	$8.40
Purchase #6	$244.80	13.751%	$278.4624	$278.46	$278.45	$278.50
Purchase #7	$28.69	12.826%	$32.3698	$32.37	$32.35	$32.40
7 purchase totals =	$888.65		$999.5420	$999.53	$999.55	$999.60