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	$63.80	11.840%	$71.3539	$71.35	$71.35	$71.40
Purchase #2	$64.62	4.104%	$67.272	$67.27	$67.25	$67.30
Purchase #3	$168.59	3.420%	$174.3558	$174.36	$174.35	$174.40
Purchase #4	$231.37	12.139%	$259.456	$259.46	$259.45	$259.50
Purchase #5	$163.45	3.331%	$168.8945	$168.89	$168.90	$168.90
Purchase #6	$22.94	7.813%	$24.7323	$24.73	$24.75	$24.70
Purchase #7	$119.51	9.359%	$130.6949	$130.69	$130.70	$130.70
7 purchase totals =	$834.28		$896.7594	$896.75	$896.75	$896.90