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	$142.79	6.288%	$151.7686	$151.77	$151.75	$151.80
Purchase #2	$53.50	11.177%	$59.4797	$59.48	$59.50	$59.50
Purchase #3	$180.92	5.765%	$191.35	$191.35	$191.35	$191.40
Purchase #4	$97.51	13.215%	$110.3959	$110.40	$110.40	$110.40
Purchase #5	$36.93	13.801%	$42.0267	$42.03	$42.05	$42.00
Purchase #6	$192.85	13.836%	$219.5327	$219.53	$219.55	$219.50
Purchase #7	$23.71	5.268%	$24.959	$24.96	$24.95	$25.00
7 purchase totals =	$728.21		$799.5126	$799.52	$799.55	$799.60