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	$209.30	10.820%	$231.9463	$231.95	$231.95	$231.90
Purchase #2	$95.59	4.763%	$100.143	$100.14	$100.15	$100.10
Purchase #3	$233.84	13.524%	$265.4645	$265.46	$265.45	$265.50
Purchase #4	$160.51	3.110%	$165.5019	$165.50	$165.50	$165.50
Purchase #5	$154.69	8.615%	$168.0165	$168.02	$168.00	$168.00
Purchase #6	$78.49	5.450%	$82.7677	$82.77	$82.75	$82.80
Purchase #7	$156.47	9.797%	$171.7994	$171.80	$171.80	$171.80
7 purchase totals =	$1,088.89		$1,185.6393	$1,185.64	$1,185.60	$1,185.60