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	$98.51	11.574%	$109.9115	$109.91	$109.90	$109.90
Purchase #2	$181.81	8.151%	$196.6293	$196.63	$196.65	$196.60
Purchase #3	$201.86	4.414%	$210.7701	$210.77	$210.75	$210.80
Purchase #4	$95.47	4.608%	$99.8693	$99.87	$99.85	$99.90
Purchase #5	$203.80	5.311%	$214.6238	$214.62	$214.60	$214.60
Purchase #6	$182.85	13.682%	$207.8675	$207.87	$207.85	$207.90
Purchase #7	$99.83	13.111%	$112.9187	$112.92	$112.90	$112.90
7 purchase totals =	$1,064.13		$1,152.5902	$1,152.59	$1,152.50	$1,152.60