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	$65.75	6.263%	$69.8679	$69.87	$69.85	$69.90
Purchase #2	$92.74	8.472%	$100.5969	$100.60	$100.60	$100.60
Purchase #3	$124.69	10.549%	$137.8435	$137.84	$137.85	$137.80
Purchase #4	$147.50	7.482%	$158.536	$158.54	$158.55	$158.50
Purchase #5	$198.70	6.465%	$211.546	$211.55	$211.55	$211.50
Purchase #6	$10.88	11.353%	$12.1152	$12.12	$12.10	$12.10
Purchase #7	$120.79	8.777%	$131.3917	$131.39	$131.40	$131.40
7 purchase totals =	$761.05		$821.8972	$821.91	$821.90	$821.80