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	$47.85	7.568%	$51.4713	$51.47	$51.45	$51.50
Purchase #2	$151.98	12.322%	$170.707	$170.71	$170.70	$170.70
Purchase #3	$243.79	11.491%	$271.8039	$271.80	$271.80	$271.80
Purchase #4	$158.38	4.121%	$164.9068	$164.91	$164.90	$164.90
Purchase #5	$86.31	3.560%	$89.3826	$89.38	$89.40	$89.40
Purchase #6	$150.74	13.617%	$171.2663	$171.27	$171.25	$171.30
Purchase #7	$184.72	5.381%	$194.6598	$194.66	$194.65	$194.70
7 purchase totals =	$1,023.77		$1,114.1977	$1,114.20	$1,114.15	$1,114.30