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	$151.30	11.107%	$168.1049	$168.10	$168.10	$168.10
Purchase #2	$80.49	11.576%	$89.8075	$89.81	$89.80	$89.80
Purchase #3	$18.57	4.172%	$19.3447	$19.34	$19.35	$19.30
Purchase #4	$94.64	10.749%	$104.8129	$104.81	$104.80	$104.80
Purchase #5	$165.28	5.221%	$173.9093	$173.91	$173.90	$173.90
Purchase #6	$201.56	11.275%	$224.2859	$224.29	$224.30	$224.30
Purchase #7	$65.44	8.616%	$71.0783	$71.08	$71.10	$71.10
7 purchase totals =	$777.28		$851.3435	$851.34	$851.35	$851.30