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	$111.29	13.763%	$126.6068	$126.61	$126.60	$126.60
Purchase #2	$178.72	5.703%	$188.9124	$188.91	$188.90	$188.90
Purchase #3	$190.96	4.791%	$200.1089	$200.11	$200.10	$200.10
Purchase #4	$68.31	12.414%	$76.79	$76.79	$76.80	$76.80
Purchase #5	$30.63	6.164%	$32.518	$32.52	$32.50	$32.50
Purchase #6	$43.30	4.648%	$45.3126	$45.31	$45.30	$45.30
Purchase #7	$104.99	3.251%	$108.4032	$108.40	$108.40	$108.40
7 purchase totals =	$728.20		$778.6519	$778.65	$778.60	$778.60