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	$115.91	9.722%	$127.1788	$127.18	$127.20	$127.20
Purchase #2	$235.33	11.220%	$261.734	$261.73	$261.75	$261.70
Purchase #3	$53.28	12.125%	$59.7402	$59.74	$59.75	$59.70
Purchase #4	$94.46	3.755%	$98.007	$98.01	$98.00	$98.00
Purchase #5	$112.36	13.174%	$127.1623	$127.16	$127.15	$127.20
Purchase #6	$140.55	13.491%	$159.5116	$159.51	$159.50	$159.50
Purchase #7	$97.40	7.838%	$105.0342	$105.03	$105.05	$105.00
7 purchase totals =	$849.29		$938.3681	$938.36	$938.40	$938.30