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	$72.28	13.535%	$82.0631	$82.06	$82.05	$82.10
Purchase #2	$88.73	9.202%	$96.8949	$96.89	$96.90	$96.90
Purchase #3	$135.30	13.330%	$153.3355	$153.34	$153.35	$153.30
Purchase #4	$57.27	5.392%	$60.358	$60.36	$60.35	$60.40
Purchase #5	$84.65	6.575%	$90.2157	$90.22	$90.20	$90.20
Purchase #6	$130.47	8.395%	$141.423	$141.42	$141.40	$141.40
Purchase #7	$108.48	13.583%	$123.2148	$123.21	$123.20	$123.20
7 purchase totals =	$677.18		$747.5050	$747.50	$747.45	$747.50