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	$181.98	10.127%	$200.4091	$200.41	$200.40	$200.40
Purchase #2	$33.49	11.851%	$37.4589	$37.46	$37.45	$37.50
Purchase #3	$241.90	10.301%	$266.8181	$266.82	$266.80	$266.80
Purchase #4	$212.72	7.596%	$228.8782	$228.88	$228.90	$228.90
Purchase #5	$7.33	10.840%	$8.1246	$8.12	$8.10	$8.10
Purchase #6	$218.55	9.174%	$238.5998	$238.60	$238.60	$238.60
Purchase #7	$122.97	13.397%	$139.4443	$139.44	$139.45	$139.40
7 purchase totals =	$1,018.94		$1,119.7330	$1,119.73	$1,119.70	$1,119.70