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	$240.30	5.299%	$253.0335	$253.03	$253.05	$253.00
Purchase #2	$230.89	5.171%	$242.8293	$242.83	$242.85	$242.80
Purchase #3	$54.62	12.397%	$61.3912	$61.39	$61.40	$61.40
Purchase #4	$219.44	6.211%	$233.0694	$233.07	$233.05	$233.10
Purchase #5	$30.75	6.745%	$32.8241	$32.82	$32.80	$32.80
Purchase #6	$237.50	4.640%	$248.52	$248.52	$248.50	$248.50
Purchase #7	$105.72	10.261%	$116.5679	$116.57	$116.55	$116.60
7 purchase totals =	$1,119.22		$1,188.2354	$1,188.23	$1,188.20	$1,188.20