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	$201.96	10.556%	$223.2789	$223.28	$223.30	$223.30
Purchase #2	$99.68	7.236%	$106.8928	$106.89	$106.90	$106.90
Purchase #3	$219.82	11.529%	$245.163	$245.16	$245.15	$245.20
Purchase #4	$35.86	3.224%	$37.0161	$37.02	$37.00	$37.00
Purchase #5	$114.98	13.554%	$130.5644	$130.56	$130.55	$130.60
Purchase #6	$180.69	8.693%	$196.3974	$196.40	$196.40	$196.40
Purchase #7	$51.31	7.847%	$55.3363	$55.34	$55.35	$55.30
7 purchase totals =	$904.30		$994.6489	$994.65	$994.65	$994.70