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	$206.54	13.738%	$234.9145	$234.91	$234.90	$234.90
Purchase #2	$66.46	7.337%	$71.3362	$71.34	$71.35	$71.30
Purchase #3	$183.78	6.743%	$196.1723	$196.17	$196.15	$196.20
Purchase #4	$79.25	7.537%	$85.2231	$85.22	$85.20	$85.20
Purchase #5	$116.26	12.732%	$131.0622	$131.06	$131.05	$131.10
Purchase #6	$68.65	7.135%	$73.5482	$73.55	$73.55	$73.50
Purchase #7	$30.75	12.377%	$34.5559	$34.56	$34.55	$34.60
7 purchase totals =	$751.69		$826.8124	$826.81	$826.75	$826.80