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	$182.84	11.830%	$204.47	$204.47	$204.45	$204.50
Purchase #2	$191.89	9.404%	$209.9353	$209.94	$209.95	$209.90
Purchase #3	$196.58	6.733%	$209.8157	$209.82	$209.80	$209.80
Purchase #4	$233.34	13.834%	$265.6203	$265.62	$265.60	$265.60
Purchase #5	$96.69	13.636%	$109.8746	$109.87	$109.85	$109.90
Purchase #6	$71.58	12.486%	$80.5175	$80.52	$80.50	$80.50
Purchase #7	$13.29	12.370%	$14.934	$14.93	$14.95	$14.90
7 purchase totals =	$986.21		$1,095.1674	$1,095.17	$1,095.10	$1,095.10