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	$142.75	5.711%	$150.9025	$150.90	$150.90	$150.90
Purchase #2	$120.46	13.245%	$136.4149	$136.41	$136.40	$136.40
Purchase #3	$92.52	13.554%	$105.0602	$105.06	$105.05	$105.10
Purchase #4	$147.72	5.311%	$155.5654	$155.57	$155.55	$155.60
Purchase #5	$37.95	7.444%	$40.775	$40.78	$40.80	$40.80
Purchase #6	$48.59	9.194%	$53.0574	$53.06	$53.05	$53.10
Purchase #7	$219.25	11.131%	$243.6547	$243.65	$243.65	$243.70
7 purchase totals =	$809.24		$885.4301	$885.43	$885.40	$885.60