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	$145.56	4.149%	$151.5993	$151.60	$151.60	$151.60
Purchase #2	$173.99	4.344%	$181.5481	$181.55	$181.55	$181.50
Purchase #3	$39.76	10.513%	$43.94	$43.94	$43.95	$43.90
Purchase #4	$182.79	12.312%	$205.2951	$205.30	$205.30	$205.30
Purchase #5	$40.38	6.199%	$42.8832	$42.88	$42.90	$42.90
Purchase #6	$110.26	13.297%	$124.9213	$124.92	$124.90	$124.90
Purchase #7	$248.65	8.748%	$270.4019	$270.40	$270.40	$270.40
7 purchase totals =	$941.39		$1,020.5889	$1,020.59	$1,020.60	$1,020.50