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	$242.28	10.487%	$267.6879	$267.69	$267.70	$267.70
Purchase #2	$201.40	10.838%	$223.2277	$223.23	$223.25	$223.20
Purchase #3	$225.25	3.680%	$233.5392	$233.54	$233.55	$233.50
Purchase #4	$59.64	12.779%	$67.2614	$67.26	$67.25	$67.30
Purchase #5	$94.28	7.807%	$101.6404	$101.64	$101.65	$101.60
Purchase #6	$91.61	7.227%	$98.2307	$98.23	$98.25	$98.20
Purchase #7	$13.26	8.411%	$14.3753	$14.38	$14.40	$14.40
7 purchase totals =	$927.72		$1,005.9626	$1,005.97	$1,006.05	$1,005.90