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	$160.28	6.744%	$171.0893	$171.09	$171.10	$171.10
Purchase #2	$52.47	10.567%	$58.0145	$58.01	$58.00	$58.00
Purchase #3	$136.56	11.304%	$151.9967	$152.00	$152.00	$152.00
Purchase #4	$54.47	8.455%	$59.0754	$59.08	$59.10	$59.10
Purchase #5	$222.29	5.608%	$234.756	$234.76	$234.75	$234.80
Purchase #6	$165.85	12.228%	$186.1301	$186.13	$186.15	$186.10
Purchase #7	$169.38	8.499%	$183.7756	$183.78	$183.80	$183.80
7 purchase totals =	$961.30		$1,044.8376	$1,044.85	$1,044.90	$1,044.90