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	$211.76	4.251%	$220.7619	$220.76	$220.75	$220.80
Purchase #2	$139.71	12.213%	$156.7728	$156.77	$156.75	$156.80
Purchase #3	$12.59	7.557%	$13.5414	$13.54	$13.55	$13.50
Purchase #4	$99.95	11.317%	$111.2613	$111.26	$111.25	$111.30
Purchase #5	$49.98	6.215%	$53.0863	$53.09	$53.10	$53.10
Purchase #6	$195.57	6.360%	$208.0083	$208.01	$208.00	$208.00
Purchase #7	$21.94	12.773%	$24.7424	$24.74	$24.75	$24.70
7 purchase totals =	$731.50		$788.1744	$788.17	$788.15	$788.20