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	$96.72	11.734%	$108.0691	$108.07	$108.05	$108.10
Purchase #2	$250.56	7.171%	$268.5277	$268.53	$268.55	$268.50
Purchase #3	$175.77	11.304%	$195.639	$195.64	$195.65	$195.60
Purchase #4	$46.58	9.559%	$51.0326	$51.03	$51.05	$51.00
Purchase #5	$134.65	12.817%	$151.9081	$151.91	$151.90	$151.90
Purchase #6	$82.53	4.832%	$86.5178	$86.52	$86.50	$86.50
Purchase #7	$64.84	10.659%	$71.7513	$71.75	$71.75	$71.80
7 purchase totals =	$851.65		$933.4456	$933.45	$933.45	$933.40