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	$92.42	3.102%	$95.2869	$95.29	$95.30	$95.30
Purchase #2	$234.84	10.433%	$259.3409	$259.34	$259.35	$259.30
Purchase #3	$141.53	12.328%	$158.9778	$158.98	$159.00	$159.00
Purchase #4	$145.33	13.795%	$165.3783	$165.38	$165.40	$165.40
Purchase #5	$17.83	12.231%	$20.0108	$20.01	$20.00	$20.00
Purchase #6	$142.93	9.409%	$156.3783	$156.38	$156.40	$156.40
Purchase #7	$81.68	11.532%	$91.0993	$91.10	$91.10	$91.10
7 purchase totals =	$856.56		$946.4723	$946.48	$946.55	$946.50