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	$225.80	4.146%	$235.1617	$235.16	$235.15	$235.20
Purchase #2	$223.40	6.597%	$238.1377	$238.14	$238.15	$238.10
Purchase #3	$123.89	8.296%	$134.1679	$134.17	$134.15	$134.20
Purchase #4	$25.41	9.847%	$27.9121	$27.91	$27.90	$27.90
Purchase #5	$191.90	4.362%	$200.2707	$200.27	$200.25	$200.30
Purchase #6	$242.80	11.606%	$270.9794	$270.98	$271.00	$271.00
Purchase #7	$67.62	5.553%	$71.3749	$71.37	$71.35	$71.40
7 purchase totals =	$1,100.82		$1,178.0044	$1,178.00	$1,177.95	$1,178.10