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	$109.61	12.538%	$123.3529	$123.35	$123.35	$123.40
Purchase #2	$145.56	3.565%	$150.7492	$150.75	$150.75	$150.70
Purchase #3	$45.60	3.241%	$47.0779	$47.08	$47.10	$47.10
Purchase #4	$146.25	4.301%	$152.5402	$152.54	$152.55	$152.50
Purchase #5	$192.50	7.758%	$207.4342	$207.43	$207.45	$207.40
Purchase #6	$55.27	7.650%	$59.4982	$59.50	$59.50	$59.50
Purchase #7	$240.31	10.187%	$264.7904	$264.79	$264.80	$264.80
7 purchase totals =	$935.10		$1,005.4430	$1,005.44	$1,005.50	$1,005.40