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	$10.33	5.370%	$10.8847	$10.88	$10.90	$10.90
Purchase #2	$145.61	11.618%	$162.527	$162.53	$162.55	$162.50
Purchase #3	$54.82	8.618%	$59.5444	$59.54	$59.55	$59.50
Purchase #4	$99.27	10.194%	$109.3896	$109.39	$109.40	$109.40
Purchase #5	$189.56	5.349%	$199.6996	$199.70	$199.70	$199.70
Purchase #6	$67.25	9.397%	$73.5695	$73.57	$73.55	$73.60
Purchase #7	$54.77	13.124%	$61.958	$61.96	$61.95	$62.00
7 purchase totals =	$621.61		$677.5728	$677.57	$677.60	$677.60