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	$38.75	4.138%	$40.3535	$40.35	$40.35	$40.40
Purchase #2	$56.96	4.808%	$59.6986	$59.70	$59.70	$59.70
Purchase #3	$214.55	8.465%	$232.7117	$232.71	$232.70	$232.70
Purchase #4	$97.69	6.164%	$103.7116	$103.71	$103.70	$103.70
Purchase #5	$58.84	4.600%	$61.5466	$61.55	$61.55	$61.50
Purchase #6	$105.56	13.514%	$119.8254	$119.83	$119.85	$119.80
Purchase #7	$81.98	4.738%	$85.8642	$85.86	$85.85	$85.90
7 purchase totals =	$654.33		$703.7116	$703.71	$703.70	$703.70