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	$101.33	7.339%	$108.7666	$108.77	$108.75	$108.80
Purchase #2	$173.29	10.366%	$191.2532	$191.25	$191.25	$191.30
Purchase #3	$72.69	10.608%	$80.401	$80.40	$80.40	$80.40
Purchase #4	$170.26	6.845%	$181.9143	$181.91	$181.90	$181.90
Purchase #5	$78.33	13.570%	$88.9594	$88.96	$88.95	$89.00
Purchase #6	$184.25	8.836%	$200.5303	$200.53	$200.55	$200.50
Purchase #7	$97.50	4.239%	$101.633	$101.63	$101.65	$101.60
7 purchase totals =	$877.65		$953.4578	$953.45	$953.45	$953.50