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	$112.38	13.253%	$127.2737	$127.27	$127.25	$127.30
Purchase #2	$238.25	5.120%	$250.4484	$250.45	$250.45	$250.40
Purchase #3	$249.82	12.463%	$280.9551	$280.96	$280.95	$281.00
Purchase #4	$180.85	9.802%	$198.5769	$198.58	$198.60	$198.60
Purchase #5	$249.58	10.476%	$275.726	$275.73	$275.75	$275.70
Purchase #6	$204.60	8.819%	$222.6437	$222.64	$222.65	$222.60
Purchase #7	$52.94	6.260%	$56.254	$56.25	$56.25	$56.30
7 purchase totals =	$1,288.42		$1,411.8778	$1,411.88	$1,411.90	$1,411.90