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	$207.49	7.612%	$223.2841	$223.28	$223.30	$223.30
Purchase #2	$75.27	4.248%	$78.4675	$78.47	$78.45	$78.50
Purchase #3	$35.44	6.445%	$37.7241	$37.72	$37.70	$37.70
Purchase #4	$112.63	7.373%	$120.9342	$120.93	$120.95	$120.90
Purchase #5	$250.60	9.151%	$273.5324	$273.53	$273.55	$273.50
Purchase #6	$175.44	10.773%	$194.3402	$194.34	$194.35	$194.30
Purchase #7	$103.82	10.197%	$114.4065	$114.41	$114.40	$114.40
7 purchase totals =	$960.69		$1,042.6890	$1,042.68	$1,042.70	$1,042.60