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	$229.51	4.340%	$239.4707	$239.47	$239.45	$239.50
Purchase #2	$67.56	13.326%	$76.563	$76.56	$76.55	$76.60
Purchase #3	$52.29	13.836%	$59.5248	$59.52	$59.50	$59.50
Purchase #4	$242.60	10.640%	$268.4126	$268.41	$268.40	$268.40
Purchase #5	$160.41	11.453%	$178.7818	$178.78	$178.80	$178.80
Purchase #6	$220.89	12.256%	$247.9623	$247.96	$247.95	$248.00
Purchase #7	$91.84	5.315%	$96.7213	$96.72	$96.70	$96.70
7 purchase totals =	$1,065.10		$1,167.4365	$1,167.42	$1,167.35	$1,167.50