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	$104.74	6.429%	$111.4737	$111.47	$111.45	$111.50
Purchase #2	$11.29	12.266%	$12.6748	$12.67	$12.65	$12.70
Purchase #3	$213.96	4.807%	$224.2451	$224.25	$224.25	$224.20
Purchase #4	$74.64	5.483%	$78.7325	$78.73	$78.75	$78.70
Purchase #5	$113.27	12.331%	$127.2373	$127.24	$127.25	$127.20
Purchase #6	$208.92	7.396%	$224.3717	$224.37	$224.35	$224.40
Purchase #7	$159.54	9.423%	$174.5735	$174.57	$174.55	$174.60
7 purchase totals =	$886.36		$953.3086	$953.30	$953.25	$953.30