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	$181.33	4.105%	$188.7736	$188.77	$188.75	$188.80
Purchase #2	$134.40	7.132%	$143.9854	$143.99	$144.00	$144.00
Purchase #3	$182.98	3.773%	$189.8838	$189.88	$189.90	$189.90
Purchase #4	$176.86	4.865%	$185.4642	$185.46	$185.45	$185.50
Purchase #5	$122.48	8.145%	$132.456	$132.46	$132.45	$132.50
Purchase #6	$69.99	11.591%	$78.1025	$78.10	$78.10	$78.10
Purchase #7	$155.65	6.331%	$165.5042	$165.50	$165.50	$165.50
7 purchase totals =	$1,023.69		$1,084.1697	$1,084.16	$1,084.15	$1,084.30