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	$170.86	9.872%	$187.7273	$187.73	$187.75	$187.70
Purchase #2	$61.61	4.244%	$64.2247	$64.22	$64.20	$64.20
Purchase #3	$36.35	3.302%	$37.5503	$37.55	$37.55	$37.60
Purchase #4	$41.55	8.457%	$45.0639	$45.06	$45.05	$45.10
Purchase #5	$196.87	13.872%	$224.1798	$224.18	$224.20	$224.20
Purchase #6	$132.70	7.333%	$142.4309	$142.43	$142.45	$142.40
Purchase #7	$79.65	4.440%	$83.1865	$83.19	$83.20	$83.20
7 purchase totals =	$719.59		$784.3634	$784.36	$784.40	$784.40