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	$49.61	12.506%	$55.8142	$55.81	$55.80	$55.80
Purchase #2	$46.79	9.259%	$51.1223	$51.12	$51.10	$51.10
Purchase #3	$231.45	4.822%	$242.6105	$242.61	$242.60	$242.60
Purchase #4	$54.47	13.394%	$61.7657	$61.77	$61.75	$61.80
Purchase #5	$250.66	6.334%	$266.5368	$266.54	$266.55	$266.50
Purchase #6	$242.48	12.136%	$271.9074	$271.91	$271.90	$271.90
Purchase #7	$109.33	7.755%	$117.8085	$117.81	$117.80	$117.80
7 purchase totals =	$984.79		$1,067.5654	$1,067.57	$1,067.50	$1,067.50