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	$138.34	10.416%	$152.7495	$152.75	$152.75	$152.70
Purchase #2	$92.31	6.523%	$98.3314	$98.33	$98.35	$98.30
Purchase #3	$118.90	13.403%	$134.8362	$134.84	$134.85	$134.80
Purchase #4	$88.32	8.211%	$95.572	$95.57	$95.55	$95.60
Purchase #5	$66.32	7.590%	$71.3537	$71.35	$71.35	$71.40
Purchase #6	$77.50	11.333%	$86.2831	$86.28	$86.30	$86.30
Purchase #7	$199.27	6.682%	$212.5852	$212.59	$212.60	$212.60
7 purchase totals =	$780.96		$851.7111	$851.71	$851.75	$851.70