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	$6.84	13.618%	$7.7715	$7.77	$7.75	$7.80
Purchase #2	$76.82	5.471%	$81.0228	$81.02	$81.00	$81.00
Purchase #3	$219.72	5.487%	$231.776	$231.78	$231.80	$231.80
Purchase #4	$44.34	5.739%	$46.8847	$46.88	$46.90	$46.90
Purchase #5	$176.78	8.139%	$191.1681	$191.17	$191.15	$191.20
Purchase #6	$156.50	9.538%	$171.427	$171.43	$171.45	$171.40
Purchase #7	$53.75	3.771%	$55.7769	$55.78	$55.80	$55.80
7 purchase totals =	$734.75		$785.8270	$785.83	$785.85	$785.90