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	$202.37	10.620%	$223.8617	$223.86	$223.85	$223.90
Purchase #2	$77.98	10.551%	$86.2077	$86.21	$86.20	$86.20
Purchase #3	$150.44	11.301%	$167.4412	$167.44	$167.45	$167.40
Purchase #4	$159.89	5.127%	$168.0876	$168.09	$168.10	$168.10
Purchase #5	$237.92	10.604%	$263.149	$263.15	$263.15	$263.10
Purchase #6	$52.43	13.532%	$59.5248	$59.52	$59.50	$59.50
Purchase #7	$141.88	5.352%	$149.4734	$149.47	$149.45	$149.50
7 purchase totals =	$1,022.91		$1,117.7454	$1,117.74	$1,117.70	$1,117.70