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	$203.55	3.179%	$210.0209	$210.02	$210.00	$210.00
Purchase #2	$100.86	4.471%	$105.3695	$105.37	$105.35	$105.40
Purchase #3	$82.69	3.863%	$85.8843	$85.88	$85.90	$85.90
Purchase #4	$168.68	13.220%	$190.9795	$190.98	$191.00	$191.00
Purchase #5	$30.60	10.804%	$33.906	$33.91	$33.90	$33.90
Purchase #6	$27.47	10.130%	$30.2527	$30.25	$30.25	$30.30
Purchase #7	$78.64	13.335%	$89.1266	$89.13	$89.15	$89.10
7 purchase totals =	$692.49		$745.5395	$745.54	$745.55	$745.60