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	$92.72	13.396%	$105.1408	$105.14	$105.15	$105.10
Purchase #2	$214.54	7.231%	$230.0534	$230.05	$230.05	$230.10
Purchase #3	$68.93	10.556%	$76.2063	$76.21	$76.20	$76.20
Purchase #4	$91.37	9.813%	$100.3361	$100.34	$100.35	$100.30
Purchase #5	$86.89	11.617%	$96.984	$96.98	$97.00	$97.00
Purchase #6	$235.62	6.666%	$251.3264	$251.33	$251.35	$251.30
Purchase #7	$165.82	13.635%	$188.4296	$188.43	$188.45	$188.40
7 purchase totals =	$955.89		$1,048.4766	$1,048.48	$1,048.55	$1,048.40