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	$134.42	5.620%	$141.9744	$141.97	$141.95	$142.00
Purchase #2	$102.25	4.346%	$106.6938	$106.69	$106.70	$106.70
Purchase #3	$154.79	3.453%	$160.1349	$160.13	$160.15	$160.10
Purchase #4	$160.76	7.478%	$172.7816	$172.78	$172.80	$172.80
Purchase #5	$198.49	5.499%	$209.405	$209.41	$209.40	$209.40
Purchase #6	$166.39	5.508%	$175.5548	$175.55	$175.55	$175.60
Purchase #7	$71.40	9.666%	$78.3015	$78.30	$78.30	$78.30
7 purchase totals =	$988.50		$1,044.8460	$1,044.83	$1,044.85	$1,044.90