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	$31.34	5.538%	$33.0756	$33.08	$33.10	$33.10
Purchase #2	$100.88	11.674%	$112.6567	$112.66	$112.65	$112.70
Purchase #3	$50.41	6.130%	$53.5001	$53.50	$53.50	$53.50
Purchase #4	$106.33	5.565%	$112.2473	$112.25	$112.25	$112.20
Purchase #5	$38.28	10.844%	$42.4311	$42.43	$42.45	$42.40
Purchase #6	$66.29	4.311%	$69.1478	$69.15	$69.15	$69.10
Purchase #7	$16.52	10.340%	$18.2282	$18.23	$18.25	$18.20
7 purchase totals =	$410.05		$441.2868	$441.30	$441.35	$441.20