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	$229.98	6.634%	$245.2369	$245.24	$245.25	$245.20
Purchase #2	$219.92	10.759%	$243.5812	$243.58	$243.60	$243.60
Purchase #3	$130.42	10.721%	$144.4023	$144.40	$144.40	$144.40
Purchase #4	$39.55	8.598%	$42.9505	$42.95	$42.95	$43.00
Purchase #5	$245.47	6.347%	$261.05	$261.05	$261.05	$261.10
Purchase #6	$105.42	4.793%	$110.4728	$110.47	$110.45	$110.50
Purchase #7	$80.80	10.547%	$89.322	$89.32	$89.30	$89.30
7 purchase totals =	$1,051.56		$1,137.0157	$1,137.01	$1,137.00	$1,137.10