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	$109.44	12.420%	$123.0324	$123.03	$123.05	$123.00
Purchase #2	$123.74	13.173%	$140.0403	$140.04	$140.05	$140.00
Purchase #3	$87.65	4.829%	$91.8826	$91.88	$91.90	$91.90
Purchase #4	$79.34	12.264%	$89.0703	$89.07	$89.05	$89.10
Purchase #5	$247.60	12.708%	$279.065	$279.07	$279.05	$279.10
Purchase #6	$126.75	12.614%	$142.7382	$142.74	$142.75	$142.70
Purchase #7	$148.68	7.139%	$159.2943	$159.29	$159.30	$159.30
7 purchase totals =	$923.20		$1,025.1231	$1,025.12	$1,025.15	$1,025.10