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	$127.88	9.645%	$140.214	$140.21	$140.20	$140.20
Purchase #2	$79.76	3.223%	$82.3307	$82.33	$82.35	$82.30
Purchase #3	$229.49	13.805%	$261.1711	$261.17	$261.15	$261.20
Purchase #4	$213.85	4.699%	$223.8988	$223.90	$223.90	$223.90
Purchase #5	$37.54	3.118%	$38.7105	$38.71	$38.70	$38.70
Purchase #6	$88.77	7.571%	$95.4908	$95.49	$95.50	$95.50
Purchase #7	$224.27	5.135%	$235.7863	$235.79	$235.80	$235.80
7 purchase totals =	$1,001.56		$1,077.6022	$1,077.60	$1,077.60	$1,077.60