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	$109.44	9.116%	$119.4166	$119.42	$119.40	$119.40
Purchase #2	$179.69	6.780%	$191.873	$191.87	$191.85	$191.90
Purchase #3	$240.81	10.125%	$265.192	$265.19	$265.20	$265.20
Purchase #4	$54.74	3.139%	$56.4583	$56.46	$56.45	$56.50
Purchase #5	$235.64	11.657%	$263.1086	$263.11	$263.10	$263.10
Purchase #6	$35.86	5.574%	$37.8588	$37.86	$37.85	$37.90
Purchase #7	$79.79	4.840%	$83.6518	$83.65	$83.65	$83.70
7 purchase totals =	$935.97		$1,017.5591	$1,017.56	$1,017.50	$1,017.70