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	$146.65	8.173%	$158.6357	$158.64	$158.65	$158.60
Purchase #2	$64.74	11.358%	$72.0932	$72.09	$72.10	$72.10
Purchase #3	$125.32	3.262%	$129.4079	$129.41	$129.40	$129.40
Purchase #4	$190.35	3.183%	$196.4088	$196.41	$196.40	$196.40
Purchase #5	$109.90	3.441%	$113.6817	$113.68	$113.70	$113.70
Purchase #6	$209.86	6.728%	$223.9794	$223.98	$224.00	$224.00
Purchase #7	$205.42	11.812%	$229.6842	$229.68	$229.70	$229.70
7 purchase totals =	$1,052.24		$1,123.8909	$1,123.89	$1,123.95	$1,123.90