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	$35.73	3.848%	$37.1049	$37.10	$37.10	$37.10
Purchase #2	$229.64	6.694%	$245.0121	$245.01	$245.00	$245.00
Purchase #3	$239.48	5.108%	$251.7126	$251.71	$251.70	$251.70
Purchase #4	$78.71	5.324%	$82.9005	$82.90	$82.90	$82.90
Purchase #5	$65.65	10.646%	$72.6391	$72.64	$72.65	$72.60
Purchase #6	$242.45	3.305%	$250.463	$250.46	$250.45	$250.50
Purchase #7	$111.73	3.539%	$115.6841	$115.68	$115.70	$115.70
7 purchase totals =	$1,003.39		$1,055.5163	$1,055.50	$1,055.50	$1,055.50