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	$187.26	9.415%	$204.8905	$204.89	$204.90	$204.90
Purchase #2	$221.46	13.164%	$250.613	$250.61	$250.60	$250.60
Purchase #3	$85.66	12.825%	$96.6459	$96.65	$96.65	$96.60
Purchase #4	$93.33	11.593%	$104.1497	$104.15	$104.15	$104.10
Purchase #5	$204.31	7.598%	$219.8335	$219.83	$219.85	$219.80
Purchase #6	$195.46	10.281%	$215.5552	$215.56	$215.55	$215.60
Purchase #7	$116.33	12.134%	$130.4455	$130.45	$130.45	$130.40
7 purchase totals =	$1,103.81		$1,222.1333	$1,222.14	$1,222.15	$1,222.00