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	$152.34	10.516%	$168.3601	$168.36	$168.35	$168.40
Purchase #2	$195.49	12.591%	$220.1041	$220.10	$220.10	$220.10
Purchase #3	$232.72	12.495%	$261.7984	$261.80	$261.80	$261.80
Purchase #4	$15.39	9.269%	$16.8165	$16.82	$16.80	$16.80
Purchase #5	$188.72	3.219%	$194.7949	$194.79	$194.80	$194.80
Purchase #6	$103.72	7.378%	$111.3725	$111.37	$111.35	$111.40
Purchase #7	$53.90	10.386%	$59.4981	$59.50	$59.50	$59.50
7 purchase totals =	$942.28		$1,032.7446	$1,032.74	$1,032.70	$1,032.80