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	$60.38	6.744%	$64.452	$64.45	$64.45	$64.50
Purchase #2	$221.89	11.339%	$247.0501	$247.05	$247.05	$247.10
Purchase #3	$157.73	11.546%	$175.9415	$175.94	$175.95	$175.90
Purchase #4	$205.90	13.582%	$233.8653	$233.87	$233.85	$233.90
Purchase #5	$52.53	4.497%	$54.8923	$54.89	$54.90	$54.90
Purchase #6	$96.73	11.103%	$107.4699	$107.47	$107.45	$107.50
Purchase #7	$96.94	6.432%	$103.1752	$103.18	$103.20	$103.20
7 purchase totals =	$892.10		$986.8463	$986.85	$986.85	$987.00