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	$14.67	10.807%	$16.2554	$16.26	$16.25	$16.30
Purchase #2	$130.95	11.562%	$146.0904	$146.09	$146.10	$146.10
Purchase #3	$149.82	13.374%	$169.8569	$169.86	$169.85	$169.90
Purchase #4	$149.98	13.156%	$169.7114	$169.71	$169.70	$169.70
Purchase #5	$65.27	10.196%	$71.9249	$71.92	$71.90	$71.90
Purchase #6	$89.31	11.718%	$99.7753	$99.78	$99.80	$99.80
Purchase #7	$98.67	4.522%	$103.1319	$103.13	$103.15	$103.10
7 purchase totals =	$698.67		$776.7462	$776.75	$776.75	$776.80