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	$33.35	13.558%	$37.8716	$37.87	$37.85	$37.90
Purchase #2	$235.85	7.589%	$253.7487	$253.75	$253.75	$253.70
Purchase #3	$64.57	11.723%	$72.1395	$72.14	$72.15	$72.10
Purchase #4	$57.53	10.469%	$63.5528	$63.55	$63.55	$63.60
Purchase #5	$92.78	11.310%	$103.2734	$103.27	$103.25	$103.30
Purchase #6	$249.36	6.239%	$264.9176	$264.92	$264.90	$264.90
Purchase #7	$203.69	7.356%	$218.6734	$218.67	$218.65	$218.70
7 purchase totals =	$937.13		$1,014.1770	$1,014.17	$1,014.10	$1,014.20