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	$79.88	7.313%	$85.7216	$85.72	$85.70	$85.70
Purchase #2	$179.87	3.353%	$185.901	$185.90	$185.90	$185.90
Purchase #3	$106.61	11.155%	$118.5023	$118.50	$118.50	$118.50
Purchase #4	$224.52	9.695%	$246.2872	$246.29	$246.30	$246.30
Purchase #5	$140.47	5.604%	$148.3419	$148.34	$148.35	$148.30
Purchase #6	$58.36	9.565%	$63.9421	$63.94	$63.95	$63.90
Purchase #7	$150.48	3.399%	$155.5948	$155.59	$155.60	$155.60
7 purchase totals =	$940.19		$1,004.2909	$1,004.28	$1,004.30	$1,004.20