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	$196.29	3.193%	$202.5575	$202.56	$202.55	$202.60
Purchase #2	$225.97	6.559%	$240.7914	$240.79	$240.80	$240.80
Purchase #3	$169.41	5.826%	$179.2798	$179.28	$179.30	$179.30
Purchase #4	$144.93	4.729%	$151.7837	$151.78	$151.80	$151.80
Purchase #5	$160.49	9.248%	$175.3321	$175.33	$175.35	$175.30
Purchase #6	$80.25	6.314%	$85.317	$85.32	$85.30	$85.30
Purchase #7	$58.60	5.668%	$61.9214	$61.92	$61.90	$61.90
7 purchase totals =	$1,035.94		$1,096.9829	$1,096.98	$1,097.00	$1,097.00