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	$200.65	4.455%	$209.589	$209.59	$209.60	$209.60
Purchase #2	$184.40	9.103%	$201.1859	$201.19	$201.20	$201.20
Purchase #3	$248.64	5.811%	$263.0885	$263.09	$263.10	$263.10
Purchase #4	$137.54	9.223%	$150.2253	$150.23	$150.25	$150.20
Purchase #5	$91.74	7.165%	$98.3132	$98.31	$98.30	$98.30
Purchase #6	$172.84	13.451%	$196.0887	$196.09	$196.10	$196.10
Purchase #7	$56.66	5.637%	$59.8539	$59.85	$59.85	$59.90
7 purchase totals =	$1,092.47		$1,178.3445	$1,178.35	$1,178.40	$1,178.40