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	$122.30	7.544%	$131.5263	$131.53	$131.55	$131.50
Purchase #2	$77.78	9.860%	$85.4491	$85.45	$85.45	$85.40
Purchase #3	$19.66	13.228%	$22.2606	$22.26	$22.25	$22.30
Purchase #4	$116.46	9.821%	$127.8975	$127.90	$127.90	$127.90
Purchase #5	$122.53	3.196%	$126.4461	$126.45	$126.45	$126.40
Purchase #6	$221.75	6.850%	$236.9399	$236.94	$236.95	$236.90
Purchase #7	$92.72	3.648%	$96.1024	$96.10	$96.10	$96.10
7 purchase totals =	$773.20		$826.6219	$826.63	$826.65	$826.50