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	$57.31	7.164%	$61.4157	$61.42	$61.40	$61.40
Purchase #2	$240.79	9.682%	$264.1033	$264.10	$264.10	$264.10
Purchase #3	$182.42	10.429%	$201.4446	$201.44	$201.45	$201.40
Purchase #4	$17.77	6.714%	$18.9631	$18.96	$18.95	$19.00
Purchase #5	$83.73	6.743%	$89.3759	$89.38	$89.40	$89.40
Purchase #6	$237.41	10.426%	$262.1624	$262.16	$262.15	$262.20
Purchase #7	$189.69	3.606%	$196.5302	$196.53	$196.55	$196.50
7 purchase totals =	$1,009.12		$1,093.9952	$1,093.99	$1,094.00	$1,094.00