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	$198.62	10.367%	$219.2109	$219.21	$219.20	$219.20
Purchase #2	$207.37	12.266%	$232.806	$232.81	$232.80	$232.80
Purchase #3	$99.48	5.824%	$105.2737	$105.27	$105.25	$105.30
Purchase #4	$41.26	11.194%	$45.8786	$45.88	$45.90	$45.90
Purchase #5	$54.60	12.596%	$61.4774	$61.48	$61.50	$61.50
Purchase #6	$47.87	8.540%	$51.9581	$51.96	$51.95	$52.00
Purchase #7	$117.56	12.147%	$131.84	$131.84	$131.85	$131.80
7 purchase totals =	$766.76		$848.4447	$848.45	$848.45	$848.50