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	$165.49	13.655%	$188.0877	$188.09	$188.10	$188.10
Purchase #2	$162.82	13.500%	$184.8007	$184.80	$184.80	$184.80
Purchase #3	$222.32	13.827%	$253.0602	$253.06	$253.05	$253.10
Purchase #4	$107.70	3.300%	$111.2541	$111.25	$111.25	$111.30
Purchase #5	$124.34	3.124%	$128.2244	$128.22	$128.20	$128.20
Purchase #6	$68.62	7.669%	$73.8825	$73.88	$73.90	$73.90
Purchase #7	$168.26	11.445%	$187.5174	$187.52	$187.50	$187.50
7 purchase totals =	$1,019.55		$1,126.8270	$1,126.82	$1,126.80	$1,126.90