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	$135.61	5.354%	$142.8706	$142.87	$142.85	$142.90
Purchase #2	$96.30	4.355%	$100.4939	$100.49	$100.50	$100.50
Purchase #3	$166.39	13.248%	$188.4333	$188.43	$188.45	$188.40
Purchase #4	$53.25	6.141%	$56.5201	$56.52	$56.50	$56.50
Purchase #5	$170.41	10.621%	$188.5092	$188.51	$188.50	$188.50
Purchase #6	$28.79	12.745%	$32.4593	$32.46	$32.45	$32.50
Purchase #7	$100.74	3.552%	$104.3183	$104.32	$104.30	$104.30
7 purchase totals =	$751.49		$813.6047	$813.60	$813.55	$813.60