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	$108.90	13.639%	$123.7529	$123.75	$123.75	$123.80
Purchase #2	$193.94	9.267%	$211.9124	$211.91	$211.90	$211.90
Purchase #3	$218.78	7.704%	$235.6348	$235.63	$235.65	$235.60
Purchase #4	$46.78	8.446%	$50.731	$50.73	$50.75	$50.70
Purchase #5	$115.46	12.840%	$130.2851	$130.29	$130.30	$130.30
Purchase #6	$155.90	6.483%	$166.007	$166.01	$166.00	$166.00
Purchase #7	$135.89	7.617%	$146.2407	$146.24	$146.25	$146.20
7 purchase totals =	$975.65		$1,064.5639	$1,064.56	$1,064.60	$1,064.50