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	$105.77	3.235%	$109.1917	$109.19	$109.20	$109.20
Purchase #2	$136.71	5.270%	$143.9146	$143.91	$143.90	$143.90
Purchase #3	$184.63	6.357%	$196.3669	$196.37	$196.35	$196.40
Purchase #4	$220.88	12.733%	$249.0047	$249.00	$249.00	$249.00
Purchase #5	$154.67	10.520%	$170.9413	$170.94	$170.95	$170.90
Purchase #6	$145.69	11.482%	$162.4181	$162.42	$162.40	$162.40
Purchase #7	$31.84	4.157%	$33.1636	$33.16	$33.15	$33.20
7 purchase totals =	$980.19		$1,065.0009	$1,064.99	$1,064.95	$1,065.00