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	$164.82	13.780%	$187.5322	$187.53	$187.55	$187.50
Purchase #2	$159.90	12.545%	$179.9595	$179.96	$179.95	$180.00
Purchase #3	$53.56	10.152%	$58.9974	$59.00	$59.00	$59.00
Purchase #4	$45.39	8.163%	$49.0952	$49.10	$49.10	$49.10
Purchase #5	$215.64	12.349%	$242.2694	$242.27	$242.25	$242.30
Purchase #6	$147.29	4.781%	$154.3319	$154.33	$154.35	$154.30
Purchase #7	$190.92	3.802%	$198.1788	$198.18	$198.20	$198.20
7 purchase totals =	$977.52		$1,070.3644	$1,070.37	$1,070.40	$1,070.40