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	$189.64	13.555%	$215.3457	$215.35	$215.35	$215.30
Purchase #2	$25.49	9.418%	$27.8906	$27.89	$27.90	$27.90
Purchase #3	$46.62	7.507%	$50.1198	$50.12	$50.10	$50.10
Purchase #4	$60.96	9.715%	$66.8823	$66.88	$66.90	$66.90
Purchase #5	$52.87	9.405%	$57.8424	$57.84	$57.85	$57.80
Purchase #6	$194.57	8.696%	$211.4898	$211.49	$211.50	$211.50
Purchase #7	$48.43	13.263%	$54.8533	$54.85	$54.85	$54.90
7 purchase totals =	$618.58		$684.4239	$684.42	$684.45	$684.40