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	$188.85	11.269%	$210.1315	$210.13	$210.15	$210.10
Purchase #2	$88.40	5.357%	$93.1356	$93.14	$93.15	$93.10
Purchase #3	$246.61	12.290%	$276.9184	$276.92	$276.90	$276.90
Purchase #4	$146.87	11.776%	$164.1654	$164.17	$164.15	$164.20
Purchase #5	$171.40	9.405%	$187.5202	$187.52	$187.50	$187.50
Purchase #6	$98.54	9.516%	$107.9171	$107.92	$107.90	$107.90
Purchase #7	$40.78	11.161%	$45.3315	$45.33	$45.35	$45.30
7 purchase totals =	$981.45		$1,085.1197	$1,085.13	$1,085.10	$1,085.00