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	$141.74	8.852%	$154.2868	$154.29	$154.30	$154.30
Purchase #2	$159.46	13.254%	$180.5948	$180.59	$180.60	$180.60
Purchase #3	$107.30	10.779%	$118.8659	$118.87	$118.85	$118.90
Purchase #4	$166.76	11.257%	$185.5322	$185.53	$185.55	$185.50
Purchase #5	$96.41	4.336%	$100.5903	$100.59	$100.60	$100.60
Purchase #6	$135.73	8.173%	$146.8232	$146.82	$146.80	$146.80
Purchase #7	$53.50	8.410%	$57.9994	$58.00	$58.00	$58.00
7 purchase totals =	$860.90		$944.6926	$944.69	$944.70	$944.70