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	$134.28	8.219%	$145.3165	$145.32	$145.30	$145.30
Purchase #2	$220.59	3.868%	$229.1224	$229.12	$229.10	$229.10
Purchase #3	$179.99	4.788%	$188.6079	$188.61	$188.60	$188.60
Purchase #4	$55.30	8.401%	$59.9458	$59.95	$59.95	$59.90
Purchase #5	$173.50	4.751%	$181.743	$181.74	$181.75	$181.70
Purchase #6	$232.45	4.188%	$242.185	$242.19	$242.20	$242.20
Purchase #7	$33.25	3.693%	$34.4779	$34.48	$34.50	$34.50
7 purchase totals =	$1,029.36		$1,081.3985	$1,081.41	$1,081.40	$1,081.30