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	$237.54	5.280%	$250.0821	$250.08	$250.10	$250.10
Purchase #2	$85.42	11.712%	$95.4244	$95.42	$95.40	$95.40
Purchase #3	$41.32	11.285%	$45.983	$45.98	$46.00	$46.00
Purchase #4	$222.39	10.517%	$245.7788	$245.78	$245.80	$245.80
Purchase #5	$91.42	3.459%	$94.5822	$94.58	$94.60	$94.60
Purchase #6	$89.76	5.259%	$94.4805	$94.48	$94.50	$94.50
Purchase #7	$55.94	6.683%	$59.6785	$59.68	$59.70	$59.70
7 purchase totals =	$823.79		$886.0095	$886.00	$886.10	$886.10