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	$27.52	3.810%	$28.5685	$28.57	$28.55	$28.60
Purchase #2	$156.51	3.833%	$162.509	$162.51	$162.50	$162.50
Purchase #3	$31.39	6.660%	$33.4806	$33.48	$33.50	$33.50
Purchase #4	$167.95	8.533%	$182.2812	$182.28	$182.30	$182.30
Purchase #5	$111.70	11.577%	$124.6315	$124.63	$124.65	$124.60
Purchase #6	$29.34	11.486%	$32.71	$32.71	$32.70	$32.70
Purchase #7	$7.77	10.120%	$8.5563	$8.56	$8.55	$8.60
7 purchase totals =	$532.18		$572.7371	$572.74	$572.75	$572.80