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	$171.41	7.765%	$184.72	$184.72	$184.70	$184.70
Purchase #2	$71.89	13.542%	$81.6253	$81.63	$81.65	$81.60
Purchase #3	$114.57	12.647%	$129.0597	$129.06	$129.05	$129.10
Purchase #4	$81.52	4.523%	$85.2071	$85.21	$85.20	$85.20
Purchase #5	$100.28	9.193%	$109.4987	$109.50	$109.50	$109.50
Purchase #6	$156.64	5.516%	$165.2803	$165.28	$165.30	$165.30
Purchase #7	$219.73	11.293%	$244.5441	$244.54	$244.55	$244.50
7 purchase totals =	$916.04		$999.9352	$999.94	$999.95	$999.90