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	$207.37	7.803%	$223.5511	$223.55	$223.55	$223.60
Purchase #2	$110.85	9.276%	$121.1324	$121.13	$121.15	$121.10
Purchase #3	$142.77	7.200%	$153.0494	$153.05	$153.05	$153.00
Purchase #4	$9.60	13.253%	$10.8723	$10.87	$10.85	$10.90
Purchase #5	$89.80	11.721%	$100.3255	$100.33	$100.35	$100.30
Purchase #6	$181.49	13.392%	$205.7951	$205.80	$205.80	$205.80
Purchase #7	$79.50	12.574%	$89.4963	$89.50	$89.50	$89.50
7 purchase totals =	$821.38		$904.2221	$904.23	$904.25	$904.20