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	$21.64	6.742%	$23.099	$23.10	$23.10	$23.10
Purchase #2	$97.72	12.333%	$109.7718	$109.77	$109.75	$109.80
Purchase #3	$148.43	11.429%	$165.3941	$165.39	$165.40	$165.40
Purchase #4	$41.51	6.827%	$44.3439	$44.34	$44.35	$44.30
Purchase #5	$26.37	5.651%	$27.8602	$27.86	$27.85	$27.90
Purchase #6	$100.94	13.253%	$114.3176	$114.32	$114.30	$114.30
Purchase #7	$217.76	5.386%	$229.4886	$229.49	$229.50	$229.50
7 purchase totals =	$654.37		$714.2752	$714.27	$714.25	$714.30