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	$221.77	9.248%	$242.2793	$242.28	$242.30	$242.30
Purchase #2	$68.52	6.315%	$72.847	$72.85	$72.85	$72.80
Purchase #3	$80.60	10.544%	$89.0985	$89.10	$89.10	$89.10
Purchase #4	$170.31	8.223%	$184.3146	$184.31	$184.30	$184.30
Purchase #5	$62.27	4.245%	$64.9134	$64.91	$64.90	$64.90
Purchase #6	$142.35	4.858%	$149.2654	$149.27	$149.25	$149.30
Purchase #7	$211.79	3.390%	$218.9697	$218.97	$218.95	$219.00
7 purchase totals =	$957.61		$1,021.6879	$1,021.69	$1,021.65	$1,021.70