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	$148.93	7.200%	$159.653	$159.65	$159.65	$159.70
Purchase #2	$156.59	9.801%	$171.9374	$171.94	$171.95	$171.90
Purchase #3	$117.86	4.766%	$123.4772	$123.48	$123.50	$123.50
Purchase #4	$69.35	10.851%	$76.8752	$76.88	$76.90	$76.90
Purchase #5	$101.84	7.229%	$109.202	$109.20	$109.20	$109.20
Purchase #6	$93.62	12.727%	$105.535	$105.54	$105.55	$105.50
Purchase #7	$224.99	10.855%	$249.4127	$249.41	$249.40	$249.40
7 purchase totals =	$913.18		$996.0925	$996.10	$996.15	$996.10