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	$150.94	9.711%	$165.5978	$165.60	$165.60	$165.60
Purchase #2	$114.56	4.220%	$119.3944	$119.39	$119.40	$119.40
Purchase #3	$232.28	6.626%	$247.6709	$247.67	$247.65	$247.70
Purchase #4	$73.63	6.482%	$78.4027	$78.40	$78.40	$78.40
Purchase #5	$226.91	12.169%	$254.5227	$254.52	$254.50	$254.50
Purchase #6	$119.72	3.424%	$123.8192	$123.82	$123.80	$123.80
Purchase #7	$199.57	3.787%	$207.1277	$207.13	$207.15	$207.10
7 purchase totals =	$1,117.61		$1,196.5354	$1,196.53	$1,196.50	$1,196.50