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	$142.29	7.204%	$152.5406	$152.54	$152.55	$152.50
Purchase #2	$143.79	9.417%	$157.3307	$157.33	$157.35	$157.30
Purchase #3	$14.69	8.286%	$15.9072	$15.91	$15.90	$15.90
Purchase #4	$174.76	8.367%	$189.3822	$189.38	$189.40	$189.40
Purchase #5	$37.37	12.496%	$42.0398	$42.04	$42.05	$42.00
Purchase #6	$228.98	9.735%	$251.2712	$251.27	$251.25	$251.30
Purchase #7	$82.72	11.350%	$92.1087	$92.11	$92.10	$92.10
7 purchase totals =	$824.60		$900.5804	$900.58	$900.60	$900.50