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	$90.81	7.276%	$97.4173	$97.42	$97.40	$97.40
Purchase #2	$115.90	9.662%	$127.0983	$127.10	$127.10	$127.10
Purchase #3	$98.60	4.841%	$103.3732	$103.37	$103.35	$103.40
Purchase #4	$137.27	10.489%	$151.6683	$151.67	$151.65	$151.70
Purchase #5	$145.25	4.331%	$151.5408	$151.54	$151.55	$151.50
Purchase #6	$172.43	5.650%	$182.1723	$182.17	$182.15	$182.20
Purchase #7	$216.90	10.698%	$240.104	$240.10	$240.10	$240.10
7 purchase totals =	$977.16		$1,053.3742	$1,053.37	$1,053.30	$1,053.40