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	$60.91	4.518%	$63.6619	$63.66	$63.65	$63.70
Purchase #2	$113.76	13.498%	$129.1153	$129.12	$129.10	$129.10
Purchase #3	$233.74	9.233%	$255.3212	$255.32	$255.30	$255.30
Purchase #4	$61.73	7.786%	$66.5363	$66.54	$66.55	$66.50
Purchase #5	$167.46	12.806%	$188.9049	$188.90	$188.90	$188.90
Purchase #6	$238.56	7.638%	$256.7812	$256.78	$256.80	$256.80
Purchase #7	$54.70	6.277%	$58.1335	$58.13	$58.15	$58.10
7 purchase totals =	$930.86		$1,018.4543	$1,018.45	$1,018.45	$1,018.40