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	$180.54	13.585%	$205.0664	$205.07	$205.05	$205.10
Purchase #2	$156.79	11.861%	$175.3869	$175.39	$175.40	$175.40
Purchase #3	$28.82	7.673%	$31.0314	$31.03	$31.05	$31.00
Purchase #4	$176.61	5.372%	$186.0975	$186.10	$186.10	$186.10
Purchase #5	$250.48	9.147%	$273.3914	$273.39	$273.40	$273.40
Purchase #6	$96.70	8.867%	$105.2744	$105.27	$105.25	$105.30
Purchase #7	$24.86	13.327%	$28.1731	$28.17	$28.15	$28.20
7 purchase totals =	$914.80		$1,004.4211	$1,004.42	$1,004.40	$1,004.50