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	$56.50	4.531%	$59.06	$59.06	$59.05	$59.10
Purchase #2	$37.67	12.187%	$42.2608	$42.26	$42.25	$42.30
Purchase #3	$116.69	11.281%	$129.8538	$129.85	$129.85	$129.90
Purchase #4	$136.46	8.701%	$148.3334	$148.33	$148.35	$148.30
Purchase #5	$195.37	13.565%	$221.8719	$221.87	$221.85	$221.90
Purchase #6	$130.28	4.630%	$136.312	$136.31	$136.30	$136.30
Purchase #7	$246.79	9.305%	$269.7538	$269.75	$269.75	$269.80
7 purchase totals =	$919.76		$1,007.4457	$1,007.43	$1,007.40	$1,007.60