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	$64.74	6.352%	$68.8523	$68.85	$68.85	$68.90
Purchase #2	$205.78	10.854%	$228.1154	$228.12	$228.10	$228.10
Purchase #3	$197.76	8.830%	$215.2222	$215.22	$215.20	$215.20
Purchase #4	$148.77	6.850%	$158.9607	$158.96	$158.95	$159.00
Purchase #5	$250.28	6.745%	$267.1614	$267.16	$267.15	$267.20
Purchase #6	$58.53	11.845%	$65.4629	$65.46	$65.45	$65.50
Purchase #7	$78.91	4.532%	$82.4862	$82.49	$82.50	$82.50
7 purchase totals =	$1,004.77		$1,086.2611	$1,086.26	$1,086.20	$1,086.40