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	$22.41	7.796%	$24.1571	$24.16	$24.15	$24.20
Purchase #2	$28.92	11.760%	$32.321	$32.32	$32.30	$32.30
Purchase #3	$141.63	11.782%	$158.3168	$158.32	$158.30	$158.30
Purchase #4	$241.34	5.780%	$255.2895	$255.29	$255.30	$255.30
Purchase #5	$246.97	4.345%	$257.7008	$257.70	$257.70	$257.70
Purchase #6	$160.73	13.481%	$182.398	$182.40	$182.40	$182.40
Purchase #7	$90.29	5.474%	$95.2325	$95.23	$95.25	$95.20
7 purchase totals =	$932.29		$1,005.4157	$1,005.42	$1,005.40	$1,005.40