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	$136.27	13.637%	$154.8531	$154.85	$154.85	$154.90
Purchase #2	$185.91	5.580%	$196.2838	$196.28	$196.30	$196.30
Purchase #3	$228.61	7.102%	$244.8459	$244.85	$244.85	$244.80
Purchase #4	$111.93	6.848%	$119.595	$119.60	$119.60	$119.60
Purchase #5	$105.81	7.132%	$113.3564	$113.36	$113.35	$113.40
Purchase #6	$33.98	6.872%	$36.3151	$36.32	$36.30	$36.30
Purchase #7	$209.27	9.124%	$228.3638	$228.36	$228.35	$228.40
7 purchase totals =	$1,011.78		$1,093.6131	$1,093.62	$1,093.60	$1,093.70