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	$204.40	5.617%	$215.8811	$215.88	$215.90	$215.90
Purchase #2	$15.68	12.326%	$17.6127	$17.61	$17.60	$17.60
Purchase #3	$95.58	11.765%	$106.825	$106.83	$106.85	$106.80
Purchase #4	$86.73	4.608%	$90.7265	$90.73	$90.75	$90.70
Purchase #5	$199.47	10.361%	$220.1371	$220.14	$220.15	$220.10
Purchase #6	$189.45	13.756%	$215.5107	$215.51	$215.50	$215.50
Purchase #7	$210.78	6.134%	$223.7092	$223.71	$223.70	$223.70
7 purchase totals =	$1,002.09		$1,090.4023	$1,090.41	$1,090.45	$1,090.30