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	$125.25	13.593%	$142.2752	$142.28	$142.30	$142.30
Purchase #2	$111.72	12.186%	$125.3342	$125.33	$125.35	$125.30
Purchase #3	$57.93	8.277%	$62.7249	$62.72	$62.70	$62.70
Purchase #4	$167.43	6.404%	$178.1522	$178.15	$178.15	$178.20
Purchase #5	$69.59	11.332%	$77.4759	$77.48	$77.50	$77.50
Purchase #6	$240.33	3.151%	$247.9028	$247.90	$247.90	$247.90
Purchase #7	$224.56	8.805%	$244.3325	$244.33	$244.35	$244.30
7 purchase totals =	$996.81		$1,078.1977	$1,078.19	$1,078.25	$1,078.20