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	$198.46	11.620%	$221.5211	$221.52	$221.50	$221.50
Purchase #2	$118.92	6.764%	$126.9637	$126.96	$126.95	$127.00
Purchase #3	$89.85	7.449%	$96.5429	$96.54	$96.55	$96.50
Purchase #4	$77.53	11.707%	$86.6064	$86.61	$86.60	$86.60
Purchase #5	$136.32	11.865%	$152.4944	$152.49	$152.50	$152.50
Purchase #6	$152.63	13.464%	$173.1801	$173.18	$173.20	$173.20
Purchase #7	$29.56	13.158%	$33.4495	$33.45	$33.45	$33.40
7 purchase totals =	$803.27		$890.7581	$890.75	$890.75	$890.70