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	$141.51	7.825%	$152.5832	$152.58	$152.60	$152.60
Purchase #2	$79.76	5.163%	$83.878	$83.88	$83.90	$83.90
Purchase #3	$217.25	5.560%	$229.3291	$229.33	$229.35	$229.30
Purchase #4	$56.60	12.325%	$63.576	$63.58	$63.60	$63.60
Purchase #5	$50.51	9.230%	$55.1721	$55.17	$55.15	$55.20
Purchase #6	$25.86	10.120%	$28.477	$28.48	$28.50	$28.50
Purchase #7	$148.83	3.280%	$153.7116	$153.71	$153.70	$153.70
7 purchase totals =	$720.32		$766.7270	$766.73	$766.80	$766.80