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	$137.81	10.704%	$152.5612	$152.56	$152.55	$152.60
Purchase #2	$150.82	7.602%	$162.2853	$162.29	$162.30	$162.30
Purchase #3	$233.83	13.287%	$264.899	$264.90	$264.90	$264.90
Purchase #4	$32.76	7.688%	$35.2786	$35.28	$35.30	$35.30
Purchase #5	$139.83	6.162%	$148.4463	$148.45	$148.45	$148.40
Purchase #6	$42.77	10.655%	$47.3271	$47.33	$47.35	$47.30
Purchase #7	$83.74	12.197%	$93.9538	$93.95	$93.95	$94.00
7 purchase totals =	$821.56		$904.7513	$904.76	$904.80	$904.80