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	$58.31	8.215%	$63.1002	$63.10	$63.10	$63.10
Purchase #2	$104.45	11.266%	$116.2173	$116.22	$116.20	$116.20
Purchase #3	$179.27	11.211%	$199.368	$199.37	$199.35	$199.40
Purchase #4	$245.27	3.782%	$254.5461	$254.55	$254.55	$254.50
Purchase #5	$208.46	12.386%	$234.2799	$234.28	$234.30	$234.30
Purchase #6	$71.57	9.304%	$78.2289	$78.23	$78.25	$78.20
Purchase #7	$97.40	8.185%	$105.3722	$105.37	$105.35	$105.40
7 purchase totals =	$964.73		$1,051.1126	$1,051.12	$1,051.10	$1,051.10