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	$58.48	11.576%	$65.2496	$65.25	$65.25	$65.20
Purchase #2	$130.63	13.620%	$148.4218	$148.42	$148.40	$148.40
Purchase #3	$10.25	6.432%	$10.9093	$10.91	$10.90	$10.90
Purchase #4	$96.57	7.132%	$103.4574	$103.46	$103.45	$103.50
Purchase #5	$81.49	9.335%	$89.0971	$89.10	$89.10	$89.10
Purchase #6	$194.55	7.503%	$209.1471	$209.15	$209.15	$209.10
Purchase #7	$130.58	12.606%	$147.0409	$147.04	$147.05	$147.00
7 purchase totals =	$702.55		$773.3232	$773.33	$773.30	$773.20