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	$38.27	13.520%	$43.4441	$43.44	$43.45	$43.40
Purchase #2	$181.54	6.800%	$193.8847	$193.88	$193.90	$193.90
Purchase #3	$120.61	6.149%	$128.0263	$128.03	$128.05	$128.00
Purchase #4	$206.56	7.757%	$222.5829	$222.58	$222.60	$222.60
Purchase #5	$99.92	6.569%	$106.4837	$106.48	$106.50	$106.50
Purchase #6	$42.74	6.825%	$45.657	$45.66	$45.65	$45.70
Purchase #7	$12.80	8.678%	$13.9108	$13.91	$13.90	$13.90
7 purchase totals =	$702.44		$753.9895	$753.98	$754.05	$754.00