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	$52.60	5.782%	$55.6413	$55.64	$55.65	$55.60
Purchase #2	$120.38	6.211%	$127.8568	$127.86	$127.85	$127.90
Purchase #3	$230.71	4.112%	$240.1968	$240.20	$240.20	$240.20
Purchase #4	$213.53	8.627%	$231.9512	$231.95	$231.95	$232.00
Purchase #5	$206.36	10.401%	$227.8235	$227.82	$227.80	$227.80
Purchase #6	$41.33	13.503%	$46.9108	$46.91	$46.90	$46.90
Purchase #7	$110.88	11.432%	$123.5558	$123.56	$123.55	$123.60
7 purchase totals =	$975.79		$1,053.9362	$1,053.94	$1,053.90	$1,054.00