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	$179.59	9.769%	$197.1341	$197.13	$197.15	$197.10
Purchase #2	$50.43	11.775%	$56.3681	$56.37	$56.35	$56.40
Purchase #3	$69.85	13.753%	$79.4565	$79.46	$79.45	$79.50
Purchase #4	$233.44	12.380%	$262.3399	$262.34	$262.35	$262.30
Purchase #5	$107.90	10.150%	$118.8519	$118.85	$118.85	$118.90
Purchase #6	$165.38	12.267%	$185.6672	$185.67	$185.65	$185.70
Purchase #7	$100.77	10.170%	$111.0183	$111.02	$111.00	$111.00
7 purchase totals =	$907.36		$1,010.8360	$1,010.84	$1,010.80	$1,010.90