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	$218.31	11.264%	$242.9004	$242.90	$242.90	$242.90
Purchase #2	$164.99	5.134%	$173.4606	$173.46	$173.45	$173.50
Purchase #3	$103.97	5.568%	$109.759	$109.76	$109.75	$109.80
Purchase #4	$170.48	5.275%	$179.4728	$179.47	$179.45	$179.50
Purchase #5	$244.32	3.672%	$253.2914	$253.29	$253.30	$253.30
Purchase #6	$53.67	5.393%	$56.5644	$56.56	$56.55	$56.60
Purchase #7	$80.92	13.556%	$91.8895	$91.89	$91.90	$91.90
7 purchase totals =	$1,036.66		$1,107.3381	$1,107.33	$1,107.30	$1,107.50