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	$171.84	4.383%	$179.3717	$179.37	$179.35	$179.40
Purchase #2	$6.53	13.408%	$7.4055	$7.41	$7.40	$7.40
Purchase #3	$157.46	5.705%	$166.4431	$166.44	$166.45	$166.40
Purchase #4	$204.48	13.414%	$231.9089	$231.91	$231.90	$231.90
Purchase #5	$107.28	3.133%	$110.6411	$110.64	$110.65	$110.60
Purchase #6	$151.48	7.297%	$162.5335	$162.53	$162.55	$162.50
Purchase #7	$178.77	13.639%	$203.1524	$203.15	$203.15	$203.20
7 purchase totals =	$977.84		$1,061.4562	$1,061.45	$1,061.45	$1,061.40