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	$192.66	3.607%	$199.6092	$199.61	$199.60	$199.60
Purchase #2	$72.46	7.216%	$77.6887	$77.69	$77.70	$77.70
Purchase #3	$209.85	6.248%	$222.9614	$222.96	$222.95	$223.00
Purchase #4	$219.88	3.419%	$227.3977	$227.40	$227.40	$227.40
Purchase #5	$227.71	13.627%	$258.74	$258.74	$258.75	$258.70
Purchase #6	$35.96	8.171%	$38.8983	$38.90	$38.90	$38.90
Purchase #7	$56.59	13.448%	$64.2002	$64.20	$64.20	$64.20
7 purchase totals =	$1,015.11		$1,089.4955	$1,089.50	$1,089.50	$1,089.50