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	$43.49	3.784%	$45.1357	$45.14	$45.15	$45.10
Purchase #2	$229.49	13.464%	$260.3885	$260.39	$260.40	$260.40
Purchase #3	$160.53	4.120%	$167.1438	$167.14	$167.15	$167.10
Purchase #4	$36.90	11.126%	$41.0055	$41.01	$41.00	$41.00
Purchase #5	$132.53	11.231%	$147.4144	$147.41	$147.40	$147.40
Purchase #6	$180.36	4.133%	$187.8143	$187.81	$187.80	$187.80
Purchase #7	$212.56	8.152%	$229.8879	$229.89	$229.90	$229.90
7 purchase totals =	$995.86		$1,078.7901	$1,078.79	$1,078.80	$1,078.70