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	$247.90	6.781%	$264.7101	$264.71	$264.70	$264.70
Purchase #2	$158.41	9.269%	$173.093	$173.09	$173.10	$173.10
Purchase #3	$88.49	12.286%	$99.3619	$99.36	$99.35	$99.40
Purchase #4	$96.32	4.839%	$100.9809	$100.98	$101.00	$101.00
Purchase #5	$90.91	13.809%	$103.4638	$103.46	$103.45	$103.50
Purchase #6	$193.67	4.796%	$202.9584	$202.96	$202.95	$203.00
Purchase #7	$134.99	4.831%	$141.5114	$141.51	$141.50	$141.50
7 purchase totals =	$1,010.69		$1,086.0795	$1,086.07	$1,086.05	$1,086.20