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	$161.27	12.381%	$181.2368	$181.24	$181.25	$181.20
Purchase #2	$118.63	5.292%	$124.9079	$124.91	$124.90	$124.90
Purchase #3	$149.65	4.401%	$156.2361	$156.24	$156.25	$156.20
Purchase #4	$196.92	4.401%	$205.5864	$205.59	$205.60	$205.60
Purchase #5	$159.71	3.859%	$165.8732	$165.87	$165.85	$165.90
Purchase #6	$153.77	7.177%	$164.8061	$164.81	$164.80	$164.80
Purchase #7	$105.54	3.795%	$109.5452	$109.55	$109.55	$109.50
7 purchase totals =	$1,045.49		$1,108.1917	$1,108.21	$1,108.20	$1,108.10