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	$174.27	12.658%	$196.3291	$196.33	$196.35	$196.30
Purchase #2	$249.79	7.266%	$267.9397	$267.94	$267.95	$267.90
Purchase #3	$132.91	13.858%	$151.3287	$151.33	$151.35	$151.30
Purchase #4	$82.48	5.133%	$86.7137	$86.71	$86.70	$86.70
Purchase #5	$248.63	5.701%	$262.8044	$262.80	$262.80	$262.80
Purchase #6	$174.74	4.540%	$182.6732	$182.67	$182.65	$182.70
Purchase #7	$68.33	6.300%	$72.6348	$72.63	$72.65	$72.60
7 purchase totals =	$1,131.15		$1,220.4236	$1,220.41	$1,220.45	$1,220.30