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	$18.52	7.263%	$19.8651	$19.87	$19.85	$19.90
Purchase #2	$134.26	13.802%	$152.7906	$152.79	$152.80	$152.80
Purchase #3	$19.80	7.685%	$21.3216	$21.32	$21.30	$21.30
Purchase #4	$130.94	8.468%	$142.028	$142.03	$142.05	$142.00
Purchase #5	$27.34	11.305%	$30.4308	$30.43	$30.45	$30.40
Purchase #6	$91.71	9.213%	$100.1592	$100.16	$100.15	$100.20
Purchase #7	$89.56	9.182%	$97.7834	$97.78	$97.80	$97.80
7 purchase totals =	$512.13		$564.3787	$564.38	$564.40	$564.40