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	$30.27	4.418%	$31.6073	$31.61	$31.60	$31.60
Purchase #2	$238.87	3.740%	$247.8037	$247.80	$247.80	$247.80
Purchase #3	$41.76	4.254%	$43.5365	$43.54	$43.55	$43.50
Purchase #4	$114.95	10.843%	$127.414	$127.41	$127.40	$127.40
Purchase #5	$250.65	7.473%	$269.3811	$269.38	$269.40	$269.40
Purchase #6	$19.49	6.717%	$20.7991	$20.80	$20.80	$20.80
Purchase #7	$33.48	10.434%	$36.9733	$36.97	$36.95	$37.00
7 purchase totals =	$729.47		$777.5150	$777.51	$777.50	$777.50