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	$49.86	7.774%	$53.7361	$53.74	$53.75	$53.70
Purchase #2	$91.64	4.334%	$95.6117	$95.61	$95.60	$95.60
Purchase #3	$114.27	13.545%	$129.7479	$129.75	$129.75	$129.70
Purchase #4	$185.96	5.640%	$196.4481	$196.45	$196.45	$196.40
Purchase #5	$225.77	5.370%	$237.8938	$237.89	$237.90	$237.90
Purchase #6	$154.73	12.380%	$173.8856	$173.89	$173.90	$173.90
Purchase #7	$167.91	10.192%	$185.0234	$185.02	$185.00	$185.00
7 purchase totals =	$990.14		$1,072.3466	$1,072.35	$1,072.35	$1,072.20