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	$37.69	8.375%	$40.8465	$40.85	$40.85	$40.80
Purchase #2	$29.59	7.789%	$31.8948	$31.89	$31.90	$31.90
Purchase #3	$24.77	3.156%	$25.5517	$25.55	$25.55	$25.60
Purchase #4	$43.73	12.654%	$49.2636	$49.26	$49.25	$49.30
Purchase #5	$16.39	11.777%	$18.3203	$18.32	$18.30	$18.30
Purchase #6	$94.71	12.324%	$106.3821	$106.38	$106.40	$106.40
Purchase #7	$127.98	7.233%	$137.2368	$137.24	$137.25	$137.20
7 purchase totals =	$374.86		$409.4958	$409.49	$409.50	$409.50