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	$29.82	8.824%	$32.4513	$32.45	$32.45	$32.50
Purchase #2	$64.26	10.694%	$71.132	$71.13	$71.15	$71.10
Purchase #3	$203.37	12.614%	$229.0231	$229.02	$229.00	$229.00
Purchase #4	$150.26	5.466%	$158.4732	$158.47	$158.45	$158.50
Purchase #5	$159.64	6.298%	$169.6941	$169.69	$169.70	$169.70
Purchase #6	$51.47	10.511%	$56.88	$56.88	$56.90	$56.90
Purchase #7	$53.26	10.415%	$58.807	$58.81	$58.80	$58.80
7 purchase totals =	$712.08		$776.4607	$776.45	$776.45	$776.50