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	$233.27	4.549%	$243.8815	$243.88	$243.90	$243.90
Purchase #2	$218.43	13.227%	$247.3217	$247.32	$247.30	$247.30
Purchase #3	$176.89	5.586%	$186.7711	$186.77	$186.75	$186.80
Purchase #4	$228.71	4.404%	$238.7824	$238.78	$238.80	$238.80
Purchase #5	$174.95	11.242%	$194.6179	$194.62	$194.60	$194.60
Purchase #6	$55.70	6.668%	$59.4141	$59.41	$59.40	$59.40
Purchase #7	$220.85	13.174%	$249.9448	$249.94	$249.95	$249.90
7 purchase totals =	$1,308.80		$1,420.7335	$1,420.72	$1,420.70	$1,420.70