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	$136.71	12.478%	$153.7687	$153.77	$153.75	$153.80
Purchase #2	$166.66	10.408%	$184.006	$184.01	$184.00	$184.00
Purchase #3	$58.97	10.360%	$65.0793	$65.08	$65.10	$65.10
Purchase #4	$145.89	13.382%	$165.413	$165.41	$165.40	$165.40
Purchase #5	$237.64	11.234%	$264.3365	$264.34	$264.35	$264.30
Purchase #6	$191.62	12.359%	$215.3023	$215.30	$215.30	$215.30
Purchase #7	$59.86	6.426%	$63.7066	$63.71	$63.70	$63.70
7 purchase totals =	$997.35		$1,111.6124	$1,111.62	$1,111.60	$1,111.60