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	$202.87	4.686%	$212.3765	$212.38	$212.40	$212.40
Purchase #2	$151.63	11.531%	$169.1145	$169.11	$169.10	$169.10
Purchase #3	$34.31	12.109%	$38.4646	$38.46	$38.45	$38.50
Purchase #4	$104.76	8.213%	$113.3639	$113.36	$113.35	$113.40
Purchase #5	$71.28	10.632%	$78.8585	$78.86	$78.85	$78.90
Purchase #6	$148.43	6.514%	$158.0987	$158.10	$158.10	$158.10
Purchase #7	$72.99	11.870%	$81.6539	$81.65	$81.65	$81.70
7 purchase totals =	$786.27		$851.9306	$851.92	$851.90	$852.10