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	$33.78	7.584%	$36.3419	$36.34	$36.35	$36.30
Purchase #2	$159.63	4.738%	$167.1933	$167.19	$167.20	$167.20
Purchase #3	$142.33	6.411%	$151.4548	$151.45	$151.45	$151.50
Purchase #4	$155.46	3.787%	$161.3473	$161.35	$161.35	$161.30
Purchase #5	$242.65	3.401%	$250.9025	$250.90	$250.90	$250.90
Purchase #6	$18.81	3.553%	$19.4783	$19.48	$19.50	$19.50
Purchase #7	$115.53	10.481%	$127.6387	$127.64	$127.65	$127.60
7 purchase totals =	$868.19		$914.3568	$914.35	$914.40	$914.30