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	$171.35	6.290%	$182.1279	$182.13	$182.15	$182.10
Purchase #2	$164.96	10.639%	$182.5101	$182.51	$182.50	$182.50
Purchase #3	$94.54	11.375%	$105.2939	$105.29	$105.30	$105.30
Purchase #4	$101.91	5.469%	$107.4835	$107.48	$107.50	$107.50
Purchase #5	$149.88	9.731%	$164.4648	$164.46	$164.45	$164.50
Purchase #6	$140.55	4.358%	$146.6752	$146.68	$146.70	$146.70
Purchase #7	$209.64	9.408%	$229.3629	$229.36	$229.35	$229.40
7 purchase totals =	$1,032.83		$1,117.9183	$1,117.91	$1,117.95	$1,118.00