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	$231.25	12.404%	$259.9343	$259.93	$259.95	$259.90
Purchase #2	$152.64	13.104%	$172.6419	$172.64	$172.65	$172.60
Purchase #3	$217.90	11.524%	$243.0108	$243.01	$243.00	$243.00
Purchase #4	$171.31	7.854%	$184.7647	$184.76	$184.75	$184.80
Purchase #5	$221.80	9.799%	$243.5342	$243.53	$243.55	$243.50
Purchase #6	$223.81	4.400%	$233.6576	$233.66	$233.65	$233.70
Purchase #7	$119.59	5.630%	$126.3229	$126.32	$126.30	$126.30
7 purchase totals =	$1,338.30		$1,463.8664	$1,463.85	$1,463.85	$1,463.80