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	$186.80	13.438%	$211.9022	$211.90	$211.90	$211.90
Purchase #2	$32.29	3.184%	$33.3181	$33.32	$33.30	$33.30
Purchase #3	$89.32	7.212%	$95.7618	$95.76	$95.75	$95.80
Purchase #4	$95.56	10.487%	$105.5814	$105.58	$105.60	$105.60
Purchase #5	$227.31	11.426%	$253.2824	$253.28	$253.30	$253.30
Purchase #6	$135.38	5.275%	$142.5213	$142.52	$142.50	$142.50
Purchase #7	$206.41	12.512%	$232.236	$232.24	$232.25	$232.20
7 purchase totals =	$973.07		$1,074.6032	$1,074.60	$1,074.60	$1,074.60