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	$49.62	5.334%	$52.2667	$52.27	$52.25	$52.30
Purchase #2	$83.89	6.600%	$89.4267	$89.43	$89.45	$89.40
Purchase #3	$102.67	12.376%	$115.3764	$115.38	$115.40	$115.40
Purchase #4	$137.71	3.168%	$142.0727	$142.07	$142.05	$142.10
Purchase #5	$52.48	5.213%	$55.2158	$55.22	$55.20	$55.20
Purchase #6	$97.61	10.549%	$107.9069	$107.91	$107.90	$107.90
Purchase #7	$209.77	12.139%	$235.234	$235.23	$235.25	$235.20
7 purchase totals =	$733.75		$797.4992	$797.51	$797.50	$797.50