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	$207.27	3.862%	$215.2748	$215.27	$215.25	$215.30
Purchase #2	$84.61	13.199%	$95.7777	$95.78	$95.80	$95.80
Purchase #3	$88.38	4.112%	$92.0142	$92.01	$92.00	$92.00
Purchase #4	$10.64	11.411%	$11.8541	$11.85	$11.85	$11.90
Purchase #5	$249.32	8.512%	$270.5421	$270.54	$270.55	$270.50
Purchase #6	$162.32	5.615%	$171.4343	$171.43	$171.45	$171.40
Purchase #7	$189.80	7.156%	$203.3821	$203.38	$203.40	$203.40
7 purchase totals =	$992.34		$1,060.2793	$1,060.26	$1,060.30	$1,060.30