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	$220.97	10.183%	$243.4714	$243.47	$243.45	$243.50
Purchase #2	$219.26	13.367%	$248.5685	$248.57	$248.55	$248.60
Purchase #3	$48.62	5.474%	$51.2815	$51.28	$51.30	$51.30
Purchase #4	$103.84	7.207%	$111.3237	$111.32	$111.30	$111.30
Purchase #5	$79.86	11.590%	$89.1158	$89.12	$89.10	$89.10
Purchase #6	$10.87	11.259%	$12.0939	$12.09	$12.10	$12.10
Purchase #7	$234.80	13.474%	$266.437	$266.44	$266.45	$266.40
7 purchase totals =	$918.22		$1,022.2918	$1,022.29	$1,022.25	$1,022.30