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	$10.70	6.324%	$11.3767	$11.38	$11.40	$11.40
Purchase #2	$98.64	6.715%	$105.2637	$105.26	$105.25	$105.30
Purchase #3	$146.85	6.853%	$156.9136	$156.91	$156.90	$156.90
Purchase #4	$221.62	13.174%	$250.8162	$250.82	$250.80	$250.80
Purchase #5	$236.29	4.194%	$246.2	$246.20	$246.20	$246.20
Purchase #6	$39.89	3.541%	$41.3025	$41.30	$41.30	$41.30
Purchase #7	$233.98	6.411%	$248.9805	$248.98	$249.00	$249.00
7 purchase totals =	$987.97		$1,060.8532	$1,060.85	$1,060.85	$1,060.90