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	$246.51	10.564%	$272.5513	$272.55	$272.55	$272.60
Purchase #2	$59.66	9.817%	$65.5168	$65.52	$65.50	$65.50
Purchase #3	$28.73	9.590%	$31.4852	$31.49	$31.50	$31.50
Purchase #4	$214.87	3.412%	$222.2014	$222.20	$222.20	$222.20
Purchase #5	$96.83	10.404%	$106.9042	$106.90	$106.90	$106.90
Purchase #6	$169.62	10.309%	$187.1061	$187.11	$187.10	$187.10
Purchase #7	$242.80	12.715%	$273.672	$273.67	$273.65	$273.70
7 purchase totals =	$1,059.02		$1,159.4370	$1,159.44	$1,159.40	$1,159.50