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	$45.43	4.717%	$47.5729	$47.57	$47.55	$47.60
Purchase #2	$118.83	12.444%	$133.6172	$133.62	$133.60	$133.60
Purchase #3	$48.61	10.786%	$53.8531	$53.85	$53.85	$53.90
Purchase #4	$179.35	3.638%	$185.8748	$185.87	$185.85	$185.90
Purchase #5	$187.76	12.500%	$211.23	$211.23	$211.25	$211.20
Purchase #6	$51.87	4.357%	$54.13	$54.13	$54.15	$54.10
Purchase #7	$10.97	5.219%	$11.5425	$11.54	$11.55	$11.50
7 purchase totals =	$642.82		$697.8205	$697.81	$697.80	$697.80