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	$27.40	3.834%	$28.4505	$28.45	$28.45	$28.50
Purchase #2	$65.56	3.371%	$67.77	$67.77	$67.75	$67.80
Purchase #3	$165.47	8.709%	$179.8808	$179.88	$179.90	$179.90
Purchase #4	$206.97	9.426%	$226.479	$226.48	$226.50	$226.50
Purchase #5	$153.32	13.173%	$173.5168	$173.52	$173.50	$173.50
Purchase #6	$74.68	12.125%	$83.735	$83.74	$83.75	$83.70
Purchase #7	$82.82	12.212%	$92.934	$92.93	$92.95	$92.90
7 purchase totals =	$776.22		$852.7661	$852.77	$852.80	$852.80