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	$179.98	6.280%	$191.2827	$191.28	$191.30	$191.30
Purchase #2	$235.59	3.624%	$244.1278	$244.13	$244.15	$244.10
Purchase #3	$141.42	6.141%	$150.1046	$150.10	$150.10	$150.10
Purchase #4	$229.31	5.621%	$242.1995	$242.20	$242.20	$242.20
Purchase #5	$220.73	13.474%	$250.4712	$250.47	$250.45	$250.50
Purchase #6	$112.43	3.616%	$116.4955	$116.50	$116.50	$116.50
Purchase #7	$32.82	3.188%	$33.8663	$33.87	$33.85	$33.90
7 purchase totals =	$1,152.28		$1,228.5476	$1,228.55	$1,228.55	$1,228.60