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	$206.92	5.394%	$218.0813	$218.08	$218.10	$218.10
Purchase #2	$143.39	13.121%	$162.2042	$162.20	$162.20	$162.20
Purchase #3	$157.34	3.272%	$162.4882	$162.49	$162.50	$162.50
Purchase #4	$96.33	3.493%	$99.6948	$99.69	$99.70	$99.70
Purchase #5	$166.34	8.190%	$179.9632	$179.96	$179.95	$180.00
Purchase #6	$107.85	3.168%	$111.2667	$111.27	$111.25	$111.30
Purchase #7	$242.99	13.280%	$275.2591	$275.26	$275.25	$275.30
7 purchase totals =	$1,121.16		$1,208.9575	$1,208.95	$1,208.95	$1,209.10