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	$212.80	7.861%	$229.5282	$229.53	$229.55	$229.50
Purchase #2	$219.69	4.792%	$230.2175	$230.22	$230.20	$230.20
Purchase #3	$40.40	11.704%	$45.1284	$45.13	$45.15	$45.10
Purchase #4	$73.81	8.588%	$80.1488	$80.15	$80.15	$80.10
Purchase #5	$238.51	3.259%	$246.283	$246.28	$246.30	$246.30
Purchase #6	$89.34	6.793%	$95.4089	$95.41	$95.40	$95.40
Purchase #7	$221.83	5.428%	$233.8709	$233.87	$233.85	$233.90
7 purchase totals =	$1,096.38		$1,160.5857	$1,160.59	$1,160.60	$1,160.50