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	$108.52	4.107%	$112.9769	$112.98	$113.00	$113.00
Purchase #2	$152.81	4.375%	$159.4954	$159.50	$159.50	$159.50
Purchase #3	$104.35	6.735%	$111.378	$111.38	$111.40	$111.40
Purchase #4	$226.54	4.113%	$235.8576	$235.86	$235.85	$235.90
Purchase #5	$131.70	12.774%	$148.5234	$148.52	$148.50	$148.50
Purchase #6	$159.85	5.487%	$168.621	$168.62	$168.60	$168.60
Purchase #7	$73.55	12.275%	$82.5783	$82.58	$82.60	$82.60
7 purchase totals =	$957.32		$1,019.4306	$1,019.44	$1,019.45	$1,019.50