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	$91.72	12.354%	$103.0511	$103.05	$103.05	$103.10
Purchase #2	$235.81	7.406%	$253.2741	$253.27	$253.25	$253.30
Purchase #3	$172.33	13.803%	$196.1167	$196.12	$196.10	$196.10
Purchase #4	$61.75	6.698%	$65.886	$65.89	$65.90	$65.90
Purchase #5	$235.89	11.806%	$263.7392	$263.74	$263.75	$263.70
Purchase #6	$119.90	13.228%	$135.7604	$135.76	$135.75	$135.80
Purchase #7	$92.81	3.810%	$96.3461	$96.35	$96.35	$96.30
7 purchase totals =	$1,010.21		$1,114.1736	$1,114.18	$1,114.15	$1,114.20