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	$235.47	10.524%	$260.2509	$260.25	$260.25	$260.30
Purchase #2	$210.99	13.172%	$238.7816	$238.78	$238.80	$238.80
Purchase #3	$90.44	7.793%	$97.488	$97.49	$97.50	$97.50
Purchase #4	$82.90	9.823%	$91.0433	$91.04	$91.05	$91.00
Purchase #5	$229.96	10.348%	$253.7563	$253.76	$253.75	$253.80
Purchase #6	$98.57	6.670%	$105.1446	$105.14	$105.15	$105.10
Purchase #7	$157.35	9.516%	$172.3234	$172.32	$172.30	$172.30
7 purchase totals =	$1,105.68		$1,218.7881	$1,218.78	$1,218.80	$1,218.80