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	$129.54	6.236%	$137.6181	$137.62	$137.60	$137.60
Purchase #2	$10.40	4.803%	$10.8995	$10.90	$10.90	$10.90
Purchase #3	$91.88	13.822%	$104.5797	$104.58	$104.60	$104.60
Purchase #4	$158.75	10.153%	$174.8679	$174.87	$174.85	$174.90
Purchase #5	$179.58	6.630%	$191.4862	$191.49	$191.50	$191.50
Purchase #6	$174.47	4.711%	$182.6893	$182.69	$182.70	$182.70
Purchase #7	$93.66	6.327%	$99.5859	$99.59	$99.60	$99.60
7 purchase totals =	$838.28		$901.7266	$901.74	$901.75	$901.80