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	$58.53	5.181%	$61.5624	$61.56	$61.55	$61.60
Purchase #2	$228.37	11.704%	$255.0984	$255.10	$255.10	$255.10
Purchase #3	$143.25	4.335%	$149.4599	$149.46	$149.45	$149.50
Purchase #4	$124.26	4.501%	$129.8529	$129.85	$129.85	$129.90
Purchase #5	$59.57	11.248%	$66.2704	$66.27	$66.25	$66.30
Purchase #6	$168.79	9.618%	$185.0242	$185.02	$185.00	$185.00
Purchase #7	$143.28	10.623%	$158.5006	$158.50	$158.50	$158.50
7 purchase totals =	$926.05		$1,005.7688	$1,005.76	$1,005.70	$1,005.90