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	$99.39	8.544%	$107.8819	$107.88	$107.90	$107.90
Purchase #2	$132.98	10.646%	$147.1371	$147.14	$147.15	$147.10
Purchase #3	$42.35	8.464%	$45.9345	$45.93	$45.95	$45.90
Purchase #4	$244.49	8.303%	$264.79	$264.79	$264.80	$264.80
Purchase #5	$147.57	13.465%	$167.4403	$167.44	$167.45	$167.40
Purchase #6	$213.87	6.149%	$227.0209	$227.02	$227.00	$227.00
Purchase #7	$86.41	4.233%	$90.0677	$90.07	$90.05	$90.10
7 purchase totals =	$967.06		$1,050.2724	$1,050.27	$1,050.30	$1,050.20