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	$165.26	13.719%	$187.932	$187.93	$187.95	$187.90
Purchase #2	$104.83	7.269%	$112.4501	$112.45	$112.45	$112.50
Purchase #3	$99.69	5.305%	$104.9786	$104.98	$105.00	$105.00
Purchase #4	$235.31	8.747%	$255.8926	$255.89	$255.90	$255.90
Purchase #5	$244.28	7.143%	$261.7289	$261.73	$261.75	$261.70
Purchase #6	$178.84	3.853%	$185.7307	$185.73	$185.75	$185.70
Purchase #7	$64.41	11.230%	$71.6432	$71.64	$71.65	$71.60
7 purchase totals =	$1,092.62		$1,180.3561	$1,180.35	$1,180.45	$1,180.30