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	$147.54	11.304%	$164.2179	$164.22	$164.20	$164.20
Purchase #2	$231.72	6.748%	$247.3565	$247.36	$247.35	$247.40
Purchase #3	$222.78	5.532%	$235.1042	$235.10	$235.10	$235.10
Purchase #4	$191.44	11.448%	$213.3561	$213.36	$213.35	$213.40
Purchase #5	$28.79	9.113%	$31.4136	$31.41	$31.40	$31.40
Purchase #6	$151.44	5.508%	$159.7813	$159.78	$159.80	$159.80
Purchase #7	$72.57	10.464%	$80.1637	$80.16	$80.15	$80.20
7 purchase totals =	$1,046.28		$1,131.3933	$1,131.39	$1,131.35	$1,131.50