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	$47.76	11.376%	$53.1932	$53.19	$53.20	$53.20
Purchase #2	$129.45	12.213%	$145.2597	$145.26	$145.25	$145.30
Purchase #3	$72.96	13.612%	$82.8913	$82.89	$82.90	$82.90
Purchase #4	$209.64	13.554%	$238.0546	$238.05	$238.05	$238.10
Purchase #5	$217.34	3.558%	$225.073	$225.07	$225.05	$225.10
Purchase #6	$70.56	13.142%	$79.833	$79.83	$79.85	$79.80
Purchase #7	$179.81	10.334%	$198.3916	$198.39	$198.40	$198.40
7 purchase totals =	$927.52		$1,022.6964	$1,022.68	$1,022.70	$1,022.80