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	$218.56	8.166%	$236.4076	$236.41	$236.40	$236.40
Purchase #2	$99.29	12.289%	$111.4917	$111.49	$111.50	$111.50
Purchase #3	$196.85	8.293%	$213.1748	$213.17	$213.15	$213.20
Purchase #4	$211.95	8.802%	$230.6058	$230.61	$230.60	$230.60
Purchase #5	$80.70	10.648%	$89.2929	$89.29	$89.30	$89.30
Purchase #6	$204.86	8.781%	$222.8488	$222.85	$222.85	$222.80
Purchase #7	$155.32	10.159%	$171.099	$171.10	$171.10	$171.10
7 purchase totals =	$1,167.53		$1,274.9206	$1,274.92	$1,274.90	$1,274.90