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	$53.73	4.832%	$56.3262	$56.33	$56.35	$56.30
Purchase #2	$10.93	5.582%	$11.5401	$11.54	$11.55	$11.50
Purchase #3	$228.65	8.607%	$248.3299	$248.33	$248.35	$248.30
Purchase #4	$205.61	13.539%	$233.4475	$233.45	$233.45	$233.40
Purchase #5	$79.80	12.825%	$90.0344	$90.03	$90.05	$90.00
Purchase #6	$138.75	10.687%	$153.5782	$153.58	$153.60	$153.60
Purchase #7	$218.37	10.370%	$241.015	$241.02	$241.00	$241.00
7 purchase totals =	$935.84		$1,034.2713	$1,034.28	$1,034.35	$1,034.10