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	$140.71	5.238%	$148.0804	$148.08	$148.10	$148.10
Purchase #2	$167.65	10.132%	$184.6363	$184.64	$184.65	$184.60
Purchase #3	$155.27	11.347%	$172.8885	$172.89	$172.90	$172.90
Purchase #4	$211.72	12.279%	$237.7171	$237.72	$237.70	$237.70
Purchase #5	$19.44	11.688%	$21.7121	$21.71	$21.70	$21.70
Purchase #6	$71.92	11.559%	$80.2332	$80.23	$80.25	$80.20
Purchase #7	$229.42	9.406%	$250.9992	$251.00	$251.00	$251.00
7 purchase totals =	$996.13		$1,096.2668	$1,096.27	$1,096.30	$1,096.20