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	$59.70	13.110%	$67.5267	$67.53	$67.55	$67.50
Purchase #2	$206.56	3.174%	$213.1162	$213.12	$213.10	$213.10
Purchase #3	$22.79	11.845%	$25.4895	$25.49	$25.50	$25.50
Purchase #4	$211.41	3.658%	$219.1434	$219.14	$219.15	$219.10
Purchase #5	$68.94	6.388%	$73.3439	$73.34	$73.35	$73.30
Purchase #6	$47.29	10.119%	$52.0753	$52.08	$52.10	$52.10
Purchase #7	$209.69	13.791%	$238.6083	$238.61	$238.60	$238.60
7 purchase totals =	$826.38		$889.3033	$889.31	$889.35	$889.20