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	$45.45	4.603%	$47.5421	$47.54	$47.55	$47.50
Purchase #2	$162.36	11.288%	$180.6872	$180.69	$180.70	$180.70
Purchase #3	$42.45	6.734%	$45.3086	$45.31	$45.30	$45.30
Purchase #4	$78.94	12.676%	$88.9464	$88.95	$88.95	$88.90
Purchase #5	$72.54	11.570%	$80.9329	$80.93	$80.95	$80.90
Purchase #6	$198.87	7.384%	$213.5546	$213.55	$213.55	$213.60
Purchase #7	$226.45	6.620%	$241.441	$241.44	$241.45	$241.40
7 purchase totals =	$827.06		$898.4128	$898.41	$898.45	$898.30