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	$163.99	13.682%	$186.4271	$186.43	$186.45	$186.40
Purchase #2	$217.74	4.553%	$227.6537	$227.65	$227.65	$227.70
Purchase #3	$233.55	12.114%	$261.8422	$261.84	$261.85	$261.80
Purchase #4	$80.47	11.454%	$89.687	$89.69	$89.70	$89.70
Purchase #5	$196.67	9.650%	$215.6487	$215.65	$215.65	$215.60
Purchase #6	$78.49	13.280%	$88.9135	$88.91	$88.90	$88.90
Purchase #7	$67.43	7.239%	$72.3113	$72.31	$72.30	$72.30
7 purchase totals =	$1,038.34		$1,142.4835	$1,142.48	$1,142.50	$1,142.40