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	$174.62	7.864%	$188.3521	$188.35	$188.35	$188.40
Purchase #2	$62.33	12.334%	$70.0178	$70.02	$70.00	$70.00
Purchase #3	$157.52	10.404%	$173.9084	$173.91	$173.90	$173.90
Purchase #4	$185.77	12.655%	$209.2792	$209.28	$209.30	$209.30
Purchase #5	$75.28	13.403%	$85.3698	$85.37	$85.35	$85.40
Purchase #6	$36.39	6.209%	$38.6495	$38.65	$38.65	$38.60
Purchase #7	$166.32	11.436%	$185.3404	$185.34	$185.35	$185.30
7 purchase totals =	$858.23		$950.9172	$950.92	$950.90	$950.90