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	$194.49	3.156%	$200.6281	$200.63	$200.65	$200.60
Purchase #2	$179.50	10.253%	$197.9041	$197.90	$197.90	$197.90
Purchase #3	$11.73	7.804%	$12.6454	$12.65	$12.65	$12.60
Purchase #4	$180.41	8.666%	$196.0443	$196.04	$196.05	$196.00
Purchase #5	$136.81	10.259%	$150.8453	$150.85	$150.85	$150.80
Purchase #6	$218.69	11.851%	$244.607	$244.61	$244.60	$244.60
Purchase #7	$57.82	11.170%	$64.2785	$64.28	$64.30	$64.30
7 purchase totals =	$979.45		$1,066.9527	$1,066.96	$1,067.00	$1,066.80