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	$173.36	9.865%	$190.462	$190.46	$190.45	$190.50
Purchase #2	$31.33	12.524%	$35.2538	$35.25	$35.25	$35.30
Purchase #3	$106.68	8.364%	$115.6027	$115.60	$115.60	$115.60
Purchase #4	$157.89	5.416%	$166.4413	$166.44	$166.45	$166.40
Purchase #5	$155.64	11.430%	$173.4297	$173.43	$173.45	$173.40
Purchase #6	$79.48	7.293%	$85.2765	$85.28	$85.30	$85.30
Purchase #7	$97.76	11.604%	$109.1041	$109.10	$109.10	$109.10
7 purchase totals =	$802.14		$875.5701	$875.56	$875.60	$875.60