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	$241.56	9.710%	$265.0155	$265.02	$265.00	$265.00
Purchase #2	$236.59	3.274%	$244.336	$244.34	$244.35	$244.30
Purchase #3	$179.60	8.244%	$194.4062	$194.41	$194.40	$194.40
Purchase #4	$127.61	9.829%	$140.1528	$140.15	$140.15	$140.20
Purchase #5	$52.48	7.600%	$56.4685	$56.47	$56.45	$56.50
Purchase #6	$211.98	4.808%	$222.172	$222.17	$222.15	$222.20
Purchase #7	$30.29	3.499%	$31.3498	$31.35	$31.35	$31.30
7 purchase totals =	$1,080.11		$1,153.9008	$1,153.91	$1,153.85	$1,153.90