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	$173.92	7.277%	$186.5762	$186.58	$186.60	$186.60
Purchase #2	$30.57	7.551%	$32.8783	$32.88	$32.90	$32.90
Purchase #3	$137.65	13.568%	$156.3264	$156.33	$156.35	$156.30
Purchase #4	$207.70	7.355%	$222.9763	$222.98	$223.00	$223.00
Purchase #5	$204.71	9.173%	$223.488	$223.49	$223.50	$223.50
Purchase #6	$70.64	11.299%	$78.6216	$78.62	$78.60	$78.60
Purchase #7	$221.53	8.282%	$239.8771	$239.88	$239.90	$239.90
7 purchase totals =	$1,046.72		$1,140.7439	$1,140.76	$1,140.85	$1,140.80