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	$230.91	4.630%	$241.6011	$241.60	$241.60	$241.60
Purchase #2	$225.39	13.200%	$255.1415	$255.14	$255.15	$255.10
Purchase #3	$242.98	13.447%	$275.6535	$275.65	$275.65	$275.70
Purchase #4	$42.31	11.369%	$47.1202	$47.12	$47.10	$47.10
Purchase #5	$151.32	3.431%	$156.5118	$156.51	$156.50	$156.50
Purchase #6	$202.28	6.813%	$216.0613	$216.06	$216.05	$216.10
Purchase #7	$113.50	6.153%	$120.4837	$120.48	$120.50	$120.50
7 purchase totals =	$1,208.69		$1,312.5731	$1,312.56	$1,312.55	$1,312.60