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	$74.82	4.810%	$78.4188	$78.42	$78.40	$78.40
Purchase #2	$249.69	5.420%	$263.2232	$263.22	$263.20	$263.20
Purchase #3	$87.56	11.474%	$97.6066	$97.61	$97.60	$97.60
Purchase #4	$40.99	13.158%	$46.3835	$46.38	$46.40	$46.40
Purchase #5	$53.44	9.132%	$58.3201	$58.32	$58.30	$58.30
Purchase #6	$131.42	9.700%	$144.1677	$144.17	$144.15	$144.20
Purchase #7	$41.91	8.821%	$45.6069	$45.61	$45.60	$45.60
7 purchase totals =	$679.83		$733.7268	$733.73	$733.65	$733.70