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	$243.52	7.422%	$261.5941	$261.59	$261.60	$261.60
Purchase #2	$189.32	13.206%	$214.3216	$214.32	$214.30	$214.30
Purchase #3	$182.92	4.539%	$191.2227	$191.22	$191.20	$191.20
Purchase #4	$203.49	10.419%	$224.6916	$224.69	$224.70	$224.70
Purchase #5	$107.85	9.843%	$118.4657	$118.47	$118.45	$118.50
Purchase #6	$81.56	4.555%	$85.2751	$85.28	$85.30	$85.30
Purchase #7	$44.35	4.741%	$46.4526	$46.45	$46.45	$46.50
7 purchase totals =	$1,053.01		$1,142.0234	$1,142.02	$1,142.00	$1,142.10