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	$80.25	7.114%	$85.959	$85.96	$85.95	$86.00
Purchase #2	$176.73	4.745%	$185.1158	$185.12	$185.10	$185.10
Purchase #3	$19.27	13.196%	$21.8129	$21.81	$21.80	$21.80
Purchase #4	$42.63	5.821%	$45.1115	$45.11	$45.10	$45.10
Purchase #5	$199.68	7.802%	$215.259	$215.26	$215.25	$215.30
Purchase #6	$93.90	5.588%	$99.1471	$99.15	$99.15	$99.10
Purchase #7	$46.37	13.554%	$52.655	$52.66	$52.65	$52.70
7 purchase totals =	$658.83		$705.0603	$705.07	$705.00	$705.10