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	$227.48	5.807%	$240.6898	$240.69	$240.70	$240.70
Purchase #2	$12.34	13.595%	$14.0176	$14.02	$14.00	$14.00
Purchase #3	$67.29	7.387%	$72.2607	$72.26	$72.25	$72.30
Purchase #4	$82.29	8.655%	$89.4122	$89.41	$89.40	$89.40
Purchase #5	$115.55	4.341%	$120.566	$120.57	$120.55	$120.60
Purchase #6	$96.82	4.566%	$101.2408	$101.24	$101.25	$101.20
Purchase #7	$111.54	13.784%	$126.9147	$126.91	$126.90	$126.90
7 purchase totals =	$713.31		$765.1018	$765.10	$765.05	$765.10