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	$99.77	7.704%	$107.4563	$107.46	$107.45	$107.50
Purchase #2	$105.27	5.376%	$110.9293	$110.93	$110.95	$110.90
Purchase #3	$101.61	7.222%	$108.9483	$108.95	$108.95	$108.90
Purchase #4	$133.32	6.328%	$141.7565	$141.76	$141.75	$141.80
Purchase #5	$161.89	13.666%	$184.0139	$184.01	$184.00	$184.00
Purchase #6	$127.42	8.229%	$137.9054	$137.91	$137.90	$137.90
Purchase #7	$244.72	9.572%	$268.1446	$268.14	$268.15	$268.10
7 purchase totals =	$974.00		$1,059.1543	$1,059.16	$1,059.15	$1,059.10