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	$91.53	8.773%	$99.5599	$99.56	$99.55	$99.60
Purchase #2	$27.67	11.107%	$30.7433	$30.74	$30.75	$30.70
Purchase #3	$75.88	12.546%	$85.3999	$85.40	$85.40	$85.40
Purchase #4	$226.29	5.840%	$239.5053	$239.51	$239.50	$239.50
Purchase #5	$146.55	6.626%	$156.2604	$156.26	$156.25	$156.30
Purchase #6	$246.65	6.686%	$263.141	$263.14	$263.15	$263.10
Purchase #7	$179.46	9.448%	$196.4154	$196.42	$196.40	$196.40
7 purchase totals =	$994.03		$1,071.0252	$1,071.03	$1,071.00	$1,071.00