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	$185.41	10.189%	$204.3014	$204.30	$204.30	$204.30
Purchase #2	$186.66	13.347%	$211.5735	$211.57	$211.55	$211.60
Purchase #3	$41.84	4.171%	$43.5851	$43.59	$43.60	$43.60
Purchase #4	$152.92	12.435%	$171.9356	$171.94	$171.95	$171.90
Purchase #5	$92.81	8.317%	$100.529	$100.53	$100.55	$100.50
Purchase #6	$28.37	13.789%	$32.2819	$32.28	$32.30	$32.30
Purchase #7	$232.41	7.438%	$249.6967	$249.70	$249.70	$249.70
7 purchase totals =	$920.42		$1,013.9032	$1,013.91	$1,013.95	$1,013.90