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	$42.48	9.303%	$46.4319	$46.43	$46.45	$46.40
Purchase #2	$85.90	6.247%	$91.2662	$91.27	$91.25	$91.30
Purchase #3	$57.76	13.326%	$65.4571	$65.46	$65.45	$65.50
Purchase #4	$150.80	11.522%	$168.1752	$168.18	$168.20	$168.20
Purchase #5	$165.45	6.524%	$176.244	$176.24	$176.25	$176.20
Purchase #6	$58.63	11.127%	$65.1538	$65.15	$65.15	$65.20
Purchase #7	$17.96	13.123%	$20.3169	$20.32	$20.30	$20.30
7 purchase totals =	$578.98		$633.0451	$633.05	$633.05	$633.10