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	$227.89	9.158%	$248.7602	$248.76	$248.75	$248.80
Purchase #2	$120.44	9.512%	$131.8963	$131.90	$131.90	$131.90
Purchase #3	$175.43	5.725%	$185.4734	$185.47	$185.45	$185.50
Purchase #4	$209.73	9.257%	$229.1447	$229.14	$229.15	$229.10
Purchase #5	$178.82	3.736%	$185.5007	$185.50	$185.50	$185.50
Purchase #6	$183.30	13.386%	$207.8365	$207.84	$207.85	$207.80
Purchase #7	$161.88	7.634%	$174.2379	$174.24	$174.25	$174.20
7 purchase totals =	$1,257.49		$1,362.8497	$1,362.85	$1,362.85	$1,362.80