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	$199.92	13.657%	$227.2231	$227.22	$227.20	$227.20
Purchase #2	$168.91	9.258%	$184.5477	$184.55	$184.55	$184.50
Purchase #3	$53.50	11.109%	$59.4433	$59.44	$59.45	$59.40
Purchase #4	$100.35	7.243%	$107.6184	$107.62	$107.60	$107.60
Purchase #5	$49.47	4.104%	$51.5002	$51.50	$51.50	$51.50
Purchase #6	$239.48	12.424%	$269.233	$269.23	$269.25	$269.20
Purchase #7	$89.44	13.565%	$101.5725	$101.57	$101.55	$101.60
7 purchase totals =	$901.07		$1,001.1382	$1,001.13	$1,001.10	$1,001.00