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	$41.40	8.449%	$44.8979	$44.90	$44.90	$44.90
Purchase #2	$96.48	13.435%	$109.4421	$109.44	$109.45	$109.40
Purchase #3	$181.90	8.174%	$196.7685	$196.77	$196.75	$196.80
Purchase #4	$127.57	5.247%	$134.2636	$134.26	$134.25	$134.30
Purchase #5	$6.37	3.747%	$6.6087	$6.61	$6.60	$6.60
Purchase #6	$78.49	13.576%	$89.1458	$89.15	$89.15	$89.10
Purchase #7	$42.77	7.353%	$45.9149	$45.91	$45.90	$45.90
7 purchase totals =	$574.98		$627.0415	$627.04	$627.00	$627.00