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	$169.65	11.671%	$189.4499	$189.45	$189.45	$189.40
Purchase #2	$51.42	4.839%	$53.9082	$53.91	$53.90	$53.90
Purchase #3	$208.35	7.437%	$223.845	$223.85	$223.85	$223.80
Purchase #4	$172.80	12.868%	$195.0359	$195.04	$195.05	$195.00
Purchase #5	$128.99	8.270%	$139.6575	$139.66	$139.65	$139.70
Purchase #6	$177.40	6.315%	$188.6028	$188.60	$188.60	$188.60
Purchase #7	$156.72	3.448%	$162.1237	$162.12	$162.10	$162.10
7 purchase totals =	$1,065.33		$1,152.6230	$1,152.63	$1,152.60	$1,152.50