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	$56.60	13.790%	$64.4051	$64.41	$64.40	$64.40
Purchase #2	$233.25	4.230%	$243.1165	$243.12	$243.10	$243.10
Purchase #3	$68.40	5.347%	$72.0573	$72.06	$72.05	$72.10
Purchase #4	$160.73	9.413%	$175.8595	$175.86	$175.85	$175.90
Purchase #5	$86.73	5.415%	$91.4264	$91.43	$91.45	$91.40
Purchase #6	$209.82	12.821%	$236.721	$236.72	$236.70	$236.70
Purchase #7	$110.37	8.230%	$119.4535	$119.45	$119.45	$119.50
7 purchase totals =	$925.90		$1,003.0393	$1,003.05	$1,003.00	$1,003.10