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	$209.62	3.544%	$217.0489	$217.05	$217.05	$217.00
Purchase #2	$232.39	8.360%	$251.8178	$251.82	$251.80	$251.80
Purchase #3	$194.73	12.432%	$218.9388	$218.94	$218.95	$218.90
Purchase #4	$114.44	11.397%	$127.4827	$127.48	$127.50	$127.50
Purchase #5	$140.38	6.865%	$150.0171	$150.02	$150.00	$150.00
Purchase #6	$102.34	13.748%	$116.4097	$116.41	$116.40	$116.40
Purchase #7	$59.64	12.507%	$67.0992	$67.10	$67.10	$67.10
7 purchase totals =	$1,053.54		$1,148.8142	$1,148.82	$1,148.80	$1,148.70