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	$166.64	7.760%	$179.5713	$179.57	$179.55	$179.60
Purchase #2	$6.59	4.697%	$6.8995	$6.90	$6.90	$6.90
Purchase #3	$67.38	9.563%	$73.8235	$73.82	$73.80	$73.80
Purchase #4	$209.53	3.226%	$216.2894	$216.29	$216.30	$216.30
Purchase #5	$37.44	12.646%	$42.1747	$42.17	$42.15	$42.20
Purchase #6	$230.49	3.260%	$238.004	$238.00	$238.00	$238.00
Purchase #7	$22.62	13.128%	$25.5896	$25.59	$25.60	$25.60
7 purchase totals =	$740.69		$782.3520	$782.34	$782.30	$782.40