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	$100.59	8.664%	$109.3051	$109.31	$109.30	$109.30
Purchase #2	$246.60	5.417%	$259.9583	$259.96	$259.95	$260.00
Purchase #3	$12.95	10.354%	$14.2908	$14.29	$14.30	$14.30
Purchase #4	$213.94	11.285%	$238.0831	$238.08	$238.10	$238.10
Purchase #5	$83.42	7.617%	$89.7741	$89.77	$89.75	$89.80
Purchase #6	$178.69	5.717%	$188.9057	$188.91	$188.90	$188.90
Purchase #7	$70.46	6.595%	$75.1068	$75.11	$75.10	$75.10
7 purchase totals =	$906.65		$975.4239	$975.43	$975.40	$975.50