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	$74.61	4.346%	$77.8526	$77.85	$77.85	$77.90
Purchase #2	$72.85	7.427%	$78.2606	$78.26	$78.25	$78.30
Purchase #3	$58.29	11.783%	$65.1583	$65.16	$65.15	$65.20
Purchase #4	$143.43	7.560%	$154.2733	$154.27	$154.25	$154.30
Purchase #5	$34.67	6.607%	$36.9606	$36.96	$36.95	$37.00
Purchase #6	$180.57	10.502%	$199.5335	$199.53	$199.55	$199.50
Purchase #7	$200.69	6.454%	$213.6425	$213.64	$213.65	$213.60
7 purchase totals =	$765.11		$825.6814	$825.67	$825.65	$825.80