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	$199.66	13.844%	$227.3009	$227.30	$227.30	$227.30
Purchase #2	$81.91	6.105%	$86.9106	$86.91	$86.90	$86.90
Purchase #3	$233.81	13.335%	$264.9886	$264.99	$265.00	$265.00
Purchase #4	$88.68	12.176%	$99.4777	$99.48	$99.50	$99.50
Purchase #5	$185.80	4.787%	$194.6942	$194.69	$194.70	$194.70
Purchase #6	$127.95	9.272%	$139.8135	$139.81	$139.80	$139.80
Purchase #7	$42.44	9.139%	$46.3186	$46.32	$46.30	$46.30
7 purchase totals =	$960.25		$1,059.5041	$1,059.50	$1,059.50	$1,059.50