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	$165.37	3.747%	$171.5664	$171.57	$171.55	$171.60
Purchase #2	$87.37	12.653%	$98.4249	$98.42	$98.40	$98.40
Purchase #3	$99.62	11.428%	$111.0046	$111.00	$111.00	$111.00
Purchase #4	$191.52	11.746%	$214.0159	$214.02	$214.00	$214.00
Purchase #5	$215.98	8.154%	$233.591	$233.59	$233.60	$233.60
Purchase #6	$207.41	11.656%	$231.5857	$231.59	$231.60	$231.60
Purchase #7	$24.59	6.825%	$26.2683	$26.27	$26.25	$26.30
7 purchase totals =	$991.86		$1,086.4568	$1,086.46	$1,086.40	$1,086.50