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	$5.63	4.545%	$5.8859	$5.89	$5.90	$5.90
Purchase #2	$68.96	3.359%	$71.2764	$71.28	$71.30	$71.30
Purchase #3	$17.32	6.603%	$18.4636	$18.46	$18.45	$18.50
Purchase #4	$107.40	3.498%	$111.1569	$111.16	$111.15	$111.20
Purchase #5	$244.72	11.560%	$273.0096	$273.01	$273.00	$273.00
Purchase #6	$166.79	6.784%	$178.105	$178.11	$178.10	$178.10
Purchase #7	$41.26	12.454%	$46.3985	$46.40	$46.40	$46.40
7 purchase totals =	$652.08		$704.2959	$704.31	$704.30	$704.40