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	$164.77	12.556%	$185.4585	$185.46	$185.45	$185.50
Purchase #2	$159.88	12.159%	$179.3198	$179.32	$179.30	$179.30
Purchase #3	$28.89	7.246%	$30.9834	$30.98	$31.00	$31.00
Purchase #4	$51.98	4.753%	$54.4506	$54.45	$54.45	$54.50
Purchase #5	$228.31	3.315%	$235.8785	$235.88	$235.90	$235.90
Purchase #6	$99.52	4.288%	$103.7874	$103.79	$103.80	$103.80
Purchase #7	$113.72	11.548%	$126.8524	$126.85	$126.85	$126.90
7 purchase totals =	$847.07		$916.7306	$916.73	$916.75	$916.90