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	$188.47	4.465%	$196.8852	$196.89	$196.90	$196.90
Purchase #2	$6.48	6.869%	$6.9251	$6.93	$6.95	$6.90
Purchase #3	$235.80	3.573%	$244.2251	$244.23	$244.25	$244.20
Purchase #4	$25.59	5.653%	$27.0366	$27.04	$27.05	$27.00
Purchase #5	$129.93	13.401%	$147.3419	$147.34	$147.35	$147.30
Purchase #6	$227.36	4.763%	$238.1892	$238.19	$238.20	$238.20
Purchase #7	$72.78	10.463%	$80.395	$80.40	$80.40	$80.40
7 purchase totals =	$886.41		$940.9981	$941.02	$941.10	$940.90