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	$219.86	7.464%	$236.2704	$236.27	$236.25	$236.30
Purchase #2	$166.48	4.251%	$173.5571	$173.56	$173.55	$173.60
Purchase #3	$5.72	10.180%	$6.3023	$6.30	$6.30	$6.30
Purchase #4	$55.26	7.192%	$59.2343	$59.23	$59.25	$59.20
Purchase #5	$49.46	4.112%	$51.4938	$51.49	$51.50	$51.50
Purchase #6	$88.57	9.806%	$97.2552	$97.26	$97.25	$97.30
Purchase #7	$55.59	7.862%	$59.9605	$59.96	$59.95	$60.00
7 purchase totals =	$640.94		$684.0736	$684.07	$684.05	$684.20