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	$144.39	4.700%	$151.1763	$151.18	$151.20	$151.20
Purchase #2	$73.39	5.545%	$77.4595	$77.46	$77.45	$77.50
Purchase #3	$111.36	11.205%	$123.8379	$123.84	$123.85	$123.80
Purchase #4	$141.37	4.248%	$147.3754	$147.38	$147.40	$147.40
Purchase #5	$117.42	9.248%	$128.279	$128.28	$128.30	$128.30
Purchase #6	$82.33	5.107%	$86.5346	$86.53	$86.55	$86.50
Purchase #7	$197.25	12.749%	$222.3974	$222.40	$222.40	$222.40
7 purchase totals =	$867.51		$937.0601	$937.07	$937.15	$937.10