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	$86.83	3.112%	$89.5321	$89.53	$89.55	$89.50
Purchase #2	$17.34	10.332%	$19.1316	$19.13	$19.15	$19.10
Purchase #3	$196.46	9.393%	$214.9135	$214.91	$214.90	$214.90
Purchase #4	$250.73	7.813%	$270.3195	$270.32	$270.30	$270.30
Purchase #5	$105.46	3.224%	$108.86	$108.86	$108.85	$108.90
Purchase #6	$52.74	11.632%	$58.8747	$58.87	$58.85	$58.90
Purchase #7	$103.37	10.225%	$113.9396	$113.94	$113.95	$113.90
7 purchase totals =	$812.93		$875.5710	$875.56	$875.55	$875.50