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	$49.52	12.815%	$55.866	$55.87	$55.85	$55.90
Purchase #2	$183.60	6.152%	$194.8951	$194.90	$194.90	$194.90
Purchase #3	$115.50	12.669%	$130.1327	$130.13	$130.15	$130.10
Purchase #4	$106.40	5.621%	$112.3807	$112.38	$112.40	$112.40
Purchase #5	$250.52	7.669%	$269.7324	$269.73	$269.75	$269.70
Purchase #6	$119.96	6.560%	$127.8294	$127.83	$127.85	$127.80
Purchase #7	$57.54	12.147%	$64.5294	$64.53	$64.55	$64.50
7 purchase totals =	$883.04		$955.3657	$955.37	$955.45	$955.30