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	$104.62	4.556%	$109.3865	$109.39	$109.40	$109.40
Purchase #2	$8.91	12.845%	$10.0545	$10.05	$10.05	$10.10
Purchase #3	$38.60	3.427%	$39.9228	$39.92	$39.90	$39.90
Purchase #4	$117.34	10.831%	$130.0491	$130.05	$130.05	$130.00
Purchase #5	$33.52	13.118%	$37.9172	$37.92	$37.90	$37.90
Purchase #6	$138.69	12.654%	$156.2398	$156.24	$156.25	$156.20
Purchase #7	$145.45	5.174%	$152.9756	$152.98	$153.00	$153.00
7 purchase totals =	$587.13		$636.5455	$636.55	$636.55	$636.50