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	$48.70	11.325%	$54.2153	$54.22	$54.20	$54.20
Purchase #2	$224.69	4.287%	$234.3225	$234.32	$234.30	$234.30
Purchase #3	$96.61	6.118%	$102.5206	$102.52	$102.50	$102.50
Purchase #4	$150.78	9.802%	$165.5595	$165.56	$165.55	$165.60
Purchase #5	$90.28	6.515%	$96.1617	$96.16	$96.15	$96.20
Purchase #6	$71.85	11.148%	$79.8598	$79.86	$79.85	$79.90
Purchase #7	$113.83	13.732%	$129.4611	$129.46	$129.45	$129.50
7 purchase totals =	$796.74		$862.1005	$862.10	$862.00	$862.20