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	$68.73	3.231%	$70.9507	$70.95	$70.95	$71.00
Purchase #2	$180.96	5.874%	$191.5896	$191.59	$191.60	$191.60
Purchase #3	$25.75	6.852%	$27.5144	$27.51	$27.50	$27.50
Purchase #4	$80.97	10.488%	$89.4621	$89.46	$89.45	$89.50
Purchase #5	$151.65	3.679%	$157.2292	$157.23	$157.25	$157.20
Purchase #6	$37.84	11.658%	$42.2514	$42.25	$42.25	$42.30
Purchase #7	$185.61	5.260%	$195.3731	$195.37	$195.35	$195.40
7 purchase totals =	$731.51		$774.3705	$774.36	$774.35	$774.50