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	$205.74	13.865%	$234.2659	$234.27	$234.25	$234.30
Purchase #2	$48.60	9.294%	$53.1169	$53.12	$53.10	$53.10
Purchase #3	$46.63	13.595%	$52.9693	$52.97	$52.95	$53.00
Purchase #4	$196.72	8.220%	$212.8904	$212.89	$212.90	$212.90
Purchase #5	$213.64	3.275%	$220.6367	$220.64	$220.65	$220.60
Purchase #6	$210.88	5.323%	$222.1051	$222.11	$222.10	$222.10
Purchase #7	$137.79	12.169%	$154.5577	$154.56	$154.55	$154.60
7 purchase totals =	$1,060.00		$1,150.5420	$1,150.56	$1,150.50	$1,150.60