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	$33.88	9.620%	$37.1393	$37.14	$37.15	$37.10
Purchase #2	$245.31	12.115%	$275.0293	$275.03	$275.05	$275.00
Purchase #3	$98.47	8.661%	$106.9985	$107.00	$107.00	$107.00
Purchase #4	$181.68	12.619%	$204.6062	$204.61	$204.60	$204.60
Purchase #5	$158.76	4.466%	$165.8502	$165.85	$165.85	$165.90
Purchase #6	$60.44	5.822%	$63.9588	$63.96	$63.95	$64.00
Purchase #7	$14.41	6.256%	$15.3115	$15.31	$15.30	$15.30
7 purchase totals =	$792.95		$868.8938	$868.90	$868.90	$868.90