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	$232.73	6.788%	$248.5277	$248.53	$248.55	$248.50
Purchase #2	$74.89	10.863%	$83.0253	$83.03	$83.05	$83.00
Purchase #3	$196.94	12.192%	$220.9509	$220.95	$220.95	$221.00
Purchase #4	$79.54	4.212%	$82.8902	$82.89	$82.90	$82.90
Purchase #5	$209.41	13.443%	$237.561	$237.56	$237.55	$237.60
Purchase #6	$72.87	12.487%	$81.9693	$81.97	$81.95	$82.00
Purchase #7	$200.31	5.588%	$211.5033	$211.50	$211.50	$211.50
7 purchase totals =	$1,066.69		$1,166.4277	$1,166.43	$1,166.45	$1,166.50