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	$94.70	5.322%	$99.7399	$99.74	$99.75	$99.70
Purchase #2	$79.48	5.215%	$83.6249	$83.62	$83.60	$83.60
Purchase #3	$99.69	4.351%	$104.0275	$104.03	$104.05	$104.00
Purchase #4	$68.48	4.343%	$71.4541	$71.45	$71.45	$71.50
Purchase #5	$232.67	7.832%	$250.8927	$250.89	$250.90	$250.90
Purchase #6	$250.28	12.495%	$281.5525	$281.55	$281.55	$281.60
Purchase #7	$7.55	3.611%	$7.8226	$7.82	$7.80	$7.80
7 purchase totals =	$832.85		$899.1142	$899.10	$899.10	$899.10