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	$245.92	7.136%	$263.4689	$263.47	$263.45	$263.50
Purchase #2	$23.55	13.742%	$26.7862	$26.79	$26.80	$26.80
Purchase #3	$54.89	12.790%	$61.9104	$61.91	$61.90	$61.90
Purchase #4	$96.54	12.364%	$108.4762	$108.48	$108.50	$108.50
Purchase #5	$35.42	7.776%	$38.1743	$38.17	$38.15	$38.20
Purchase #6	$135.31	5.545%	$142.8129	$142.81	$142.80	$142.80
Purchase #7	$70.42	4.399%	$73.5178	$73.52	$73.50	$73.50
7 purchase totals =	$662.05		$715.1467	$715.15	$715.10	$715.20