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	$119.57	7.573%	$128.625	$128.63	$128.65	$128.60
Purchase #2	$104.52	6.261%	$111.064	$111.06	$111.05	$111.10
Purchase #3	$47.41	7.699%	$51.0601	$51.06	$51.05	$51.10
Purchase #4	$6.89	6.650%	$7.3482	$7.35	$7.35	$7.30
Purchase #5	$222.86	4.423%	$232.7171	$232.72	$232.70	$232.70
Purchase #6	$30.92	6.308%	$32.8704	$32.87	$32.85	$32.90
Purchase #7	$161.31	9.565%	$176.7393	$176.74	$176.75	$176.70
7 purchase totals =	$693.48		$740.4241	$740.43	$740.40	$740.40