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	$176.91	4.486%	$184.8462	$184.85	$184.85	$184.80
Purchase #2	$174.60	6.805%	$186.4815	$186.48	$186.50	$186.50
Purchase #3	$92.97	7.851%	$100.2691	$100.27	$100.25	$100.30
Purchase #4	$92.97	11.306%	$103.4812	$103.48	$103.50	$103.50
Purchase #5	$235.60	6.241%	$250.3038	$250.30	$250.30	$250.30
Purchase #6	$168.82	9.519%	$184.89	$184.89	$184.90	$184.90
Purchase #7	$243.26	9.617%	$266.6543	$266.65	$266.65	$266.70
7 purchase totals =	$1,185.13		$1,276.9261	$1,276.92	$1,276.95	$1,277.00