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	$184.79	7.199%	$198.093	$198.09	$198.10	$198.10
Purchase #2	$192.51	3.552%	$199.348	$199.35	$199.35	$199.30
Purchase #3	$89.82	6.673%	$95.8137	$95.81	$95.80	$95.80
Purchase #4	$121.97	7.407%	$131.0043	$131.00	$131.00	$131.00
Purchase #5	$91.94	8.140%	$99.4239	$99.42	$99.40	$99.40
Purchase #6	$68.43	3.829%	$71.0502	$71.05	$71.05	$71.10
Purchase #7	$203.92	3.766%	$211.5996	$211.60	$211.60	$211.60
7 purchase totals =	$953.38		$1,006.3327	$1,006.32	$1,006.30	$1,006.30