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	$89.40	5.463%	$94.2839	$94.28	$94.30	$94.30
Purchase #2	$70.52	10.760%	$78.108	$78.11	$78.10	$78.10
Purchase #3	$250.64	9.459%	$274.348	$274.35	$274.35	$274.30
Purchase #4	$241.75	5.646%	$255.3992	$255.40	$255.40	$255.40
Purchase #5	$155.44	3.113%	$160.2788	$160.28	$160.30	$160.30
Purchase #6	$103.50	8.669%	$112.4724	$112.47	$112.45	$112.50
Purchase #7	$171.80	3.160%	$177.2289	$177.23	$177.25	$177.20
7 purchase totals =	$1,083.05		$1,152.1192	$1,152.12	$1,152.15	$1,152.10