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	$236.83	7.280%	$254.0712	$254.07	$254.05	$254.10
Purchase #2	$9.64	11.392%	$10.7382	$10.74	$10.75	$10.70
Purchase #3	$50.71	3.325%	$52.3961	$52.40	$52.40	$52.40
Purchase #4	$29.26	11.445%	$32.6088	$32.61	$32.60	$32.60
Purchase #5	$176.36	8.483%	$191.3206	$191.32	$191.30	$191.30
Purchase #6	$165.71	11.831%	$185.3152	$185.32	$185.30	$185.30
Purchase #7	$92.25	4.843%	$96.7177	$96.72	$96.70	$96.70
7 purchase totals =	$760.76		$823.1678	$823.18	$823.10	$823.10