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	$192.83	3.119%	$198.8444	$198.84	$198.85	$198.80
Purchase #2	$8.65	3.113%	$8.9193	$8.92	$8.90	$8.90
Purchase #3	$86.63	3.853%	$89.9679	$89.97	$89.95	$90.00
Purchase #4	$97.32	6.544%	$103.6886	$103.69	$103.70	$103.70
Purchase #5	$72.73	11.673%	$81.2198	$81.22	$81.20	$81.20
Purchase #6	$57.73	6.604%	$61.5425	$61.54	$61.55	$61.50
Purchase #7	$43.44	11.174%	$48.294	$48.29	$48.30	$48.30
7 purchase totals =	$559.33		$592.4765	$592.47	$592.45	$592.40