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	$42.41	10.663%	$46.9322	$46.93	$46.95	$46.90
Purchase #2	$49.76	7.616%	$53.5497	$53.55	$53.55	$53.50
Purchase #3	$42.98	6.623%	$45.8266	$45.83	$45.85	$45.80
Purchase #4	$161.46	10.778%	$178.8622	$178.86	$178.85	$178.90
Purchase #5	$77.61	12.422%	$87.2507	$87.25	$87.25	$87.30
Purchase #6	$212.63	4.588%	$222.3855	$222.39	$222.40	$222.40
Purchase #7	$172.87	4.822%	$181.2058	$181.21	$181.20	$181.20
7 purchase totals =	$759.72		$816.0127	$816.02	$816.05	$816.00