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	$106.33	5.273%	$111.9368	$111.94	$111.95	$111.90
Purchase #2	$48.90	12.151%	$54.8418	$54.84	$54.85	$54.80
Purchase #3	$61.99	8.144%	$67.0385	$67.04	$67.05	$67.00
Purchase #4	$196.27	7.285%	$210.5683	$210.57	$210.55	$210.60
Purchase #5	$182.49	4.648%	$190.9721	$190.97	$190.95	$191.00
Purchase #6	$125.51	13.481%	$142.43	$142.43	$142.45	$142.40
Purchase #7	$92.29	4.749%	$96.6729	$96.67	$96.65	$96.70
7 purchase totals =	$813.78		$874.4604	$874.46	$874.45	$874.40