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	$172.42	3.401%	$178.284	$178.28	$178.30	$178.30
Purchase #2	$118.98	7.350%	$127.725	$127.73	$127.75	$127.70
Purchase #3	$130.27	6.142%	$138.2712	$138.27	$138.25	$138.30
Purchase #4	$161.33	11.722%	$180.2411	$180.24	$180.25	$180.20
Purchase #5	$38.58	13.455%	$43.7709	$43.77	$43.75	$43.80
Purchase #6	$160.87	6.506%	$171.3362	$171.34	$171.35	$171.30
Purchase #7	$213.66	8.380%	$231.5647	$231.56	$231.55	$231.60
7 purchase totals =	$996.11		$1,071.1931	$1,071.19	$1,071.20	$1,071.20