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	$229.81	4.560%	$240.2893	$240.29	$240.30	$240.30
Purchase #2	$89.77	11.701%	$100.274	$100.27	$100.25	$100.30
Purchase #3	$103.91	11.407%	$115.763	$115.76	$115.75	$115.80
Purchase #4	$65.33	11.277%	$72.6973	$72.70	$72.70	$72.70
Purchase #5	$217.52	13.776%	$247.4856	$247.49	$247.50	$247.50
Purchase #6	$160.48	13.858%	$182.7193	$182.72	$182.70	$182.70
Purchase #7	$99.90	13.301%	$113.1877	$113.19	$113.20	$113.20
7 purchase totals =	$966.72		$1,072.4162	$1,072.42	$1,072.40	$1,072.50