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	$232.48	9.308%	$254.1192	$254.12	$254.10	$254.10
Purchase #2	$144.31	3.298%	$149.0693	$149.07	$149.05	$149.10
Purchase #3	$147.40	12.112%	$165.2531	$165.25	$165.25	$165.30
Purchase #4	$32.75	13.718%	$37.2426	$37.24	$37.25	$37.20
Purchase #5	$32.44	10.309%	$35.7842	$35.78	$35.80	$35.80
Purchase #6	$221.83	6.601%	$236.473	$236.47	$236.45	$236.50
Purchase #7	$140.58	11.160%	$156.2687	$156.27	$156.25	$156.30
7 purchase totals =	$951.79		$1,034.2101	$1,034.20	$1,034.15	$1,034.30