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	$148.85	12.709%	$167.7673	$167.77	$167.75	$167.80
Purchase #2	$108.45	6.619%	$115.6283	$115.63	$115.65	$115.60
Purchase #3	$45.33	12.519%	$51.0049	$51.00	$51.00	$51.00
Purchase #4	$127.83	11.327%	$142.3093	$142.31	$142.30	$142.30
Purchase #5	$132.37	12.441%	$148.8382	$148.84	$148.85	$148.80
Purchase #6	$138.81	4.797%	$145.4687	$145.47	$145.45	$145.50
Purchase #7	$240.69	13.873%	$274.0809	$274.08	$274.10	$274.10
7 purchase totals =	$942.33		$1,045.0976	$1,045.10	$1,045.10	$1,045.10