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	$229.98	13.833%	$261.7931	$261.79	$261.80	$261.80
Purchase #2	$36.31	13.767%	$41.3088	$41.31	$41.30	$41.30
Purchase #3	$94.86	9.621%	$103.9865	$103.99	$104.00	$104.00
Purchase #4	$116.76	7.481%	$125.4948	$125.49	$125.50	$125.50
Purchase #5	$178.70	11.103%	$198.5411	$198.54	$198.55	$198.50
Purchase #6	$241.32	13.459%	$273.7993	$273.80	$273.80	$273.80
Purchase #7	$177.68	7.729%	$191.4129	$191.41	$191.40	$191.40
7 purchase totals =	$1,075.61		$1,196.3365	$1,196.33	$1,196.35	$1,196.30