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	$247.81	5.377%	$261.1347	$261.13	$261.15	$261.10
Purchase #2	$34.25	8.548%	$37.1777	$37.18	$37.20	$37.20
Purchase #3	$85.96	6.579%	$91.6153	$91.62	$91.60	$91.60
Purchase #4	$91.60	10.792%	$101.4855	$101.49	$101.50	$101.50
Purchase #5	$140.72	3.496%	$145.6396	$145.64	$145.65	$145.60
Purchase #6	$128.85	9.638%	$141.2686	$141.27	$141.25	$141.30
Purchase #7	$238.79	12.280%	$268.1134	$268.11	$268.10	$268.10
7 purchase totals =	$967.98		$1,046.4348	$1,046.44	$1,046.45	$1,046.40