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	$230.88	10.568%	$255.2794	$255.28	$255.30	$255.30
Purchase #2	$42.34	13.327%	$47.9827	$47.98	$48.00	$48.00
Purchase #3	$58.48	13.334%	$66.2777	$66.28	$66.30	$66.30
Purchase #4	$166.83	10.632%	$184.5674	$184.57	$184.55	$184.60
Purchase #5	$226.77	8.805%	$246.7371	$246.74	$246.75	$246.70
Purchase #6	$84.64	7.689%	$91.148	$91.15	$91.15	$91.10
Purchase #7	$145.89	11.162%	$162.1742	$162.17	$162.15	$162.20
7 purchase totals =	$955.83		$1,054.1665	$1,054.17	$1,054.20	$1,054.20