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	$49.36	8.432%	$53.522	$53.52	$53.50	$53.50
Purchase #2	$134.92	3.780%	$140.02	$140.02	$140.00	$140.00
Purchase #3	$239.33	6.848%	$255.7193	$255.72	$255.70	$255.70
Purchase #4	$221.67	5.446%	$233.7421	$233.74	$233.75	$233.70
Purchase #5	$25.67	4.801%	$26.9024	$26.90	$26.90	$26.90
Purchase #6	$182.60	7.567%	$196.4173	$196.42	$196.40	$196.40
Purchase #7	$215.86	11.546%	$240.7832	$240.78	$240.80	$240.80
7 purchase totals =	$1,069.41		$1,147.1063	$1,147.10	$1,147.05	$1,147.00