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	$193.90	8.501%	$210.3834	$210.38	$210.40	$210.40
Purchase #2	$68.86	13.761%	$78.3358	$78.34	$78.35	$78.30
Purchase #3	$217.27	12.864%	$245.2196	$245.22	$245.20	$245.20
Purchase #4	$64.57	7.296%	$69.281	$69.28	$69.30	$69.30
Purchase #5	$170.26	9.265%	$186.0346	$186.03	$186.05	$186.00
Purchase #6	$211.30	13.722%	$240.2946	$240.29	$240.30	$240.30
Purchase #7	$85.88	4.166%	$89.4578	$89.46	$89.45	$89.50
7 purchase totals =	$1,012.04		$1,119.0068	$1,119.00	$1,119.05	$1,119.00