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	$54.90	12.766%	$61.9085	$61.91	$61.90	$61.90
Purchase #2	$76.26	13.416%	$86.491	$86.49	$86.50	$86.50
Purchase #3	$144.74	9.795%	$158.9173	$158.92	$158.90	$158.90
Purchase #4	$89.76	10.148%	$98.8688	$98.87	$98.85	$98.90
Purchase #5	$32.96	6.690%	$35.165	$35.17	$35.15	$35.20
Purchase #6	$86.44	5.732%	$91.3947	$91.39	$91.40	$91.40
Purchase #7	$154.67	4.650%	$161.8622	$161.86	$161.85	$161.90
7 purchase totals =	$639.73		$694.6075	$694.61	$694.55	$694.70