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	$161.50	8.318%	$174.9336	$174.93	$174.95	$174.90
Purchase #2	$16.56	3.804%	$17.1899	$17.19	$17.20	$17.20
Purchase #3	$79.29	3.220%	$81.8431	$81.84	$81.85	$81.80
Purchase #4	$40.29	6.540%	$42.925	$42.93	$42.95	$42.90
Purchase #5	$93.39	10.152%	$102.871	$102.87	$102.85	$102.90
Purchase #6	$42.27	11.738%	$47.2317	$47.23	$47.25	$47.20
Purchase #7	$61.80	5.707%	$65.3269	$65.33	$65.35	$65.30
7 purchase totals =	$495.10		$532.3212	$532.32	$532.40	$532.20