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	$104.80	7.264%	$112.4127	$112.41	$112.40	$112.40
Purchase #2	$202.83	9.820%	$222.7479	$222.75	$222.75	$222.70
Purchase #3	$62.30	8.683%	$67.7095	$67.71	$67.70	$67.70
Purchase #4	$234.27	12.799%	$264.2542	$264.25	$264.25	$264.30
Purchase #5	$187.55	13.266%	$212.4304	$212.43	$212.45	$212.40
Purchase #6	$143.87	4.500%	$150.3442	$150.34	$150.35	$150.30
Purchase #7	$163.89	9.501%	$179.4612	$179.46	$179.45	$179.50
7 purchase totals =	$1,099.51		$1,209.3601	$1,209.35	$1,209.35	$1,209.30