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	$100.43	12.642%	$113.1264	$113.13	$113.15	$113.10
Purchase #2	$174.69	4.551%	$182.6401	$182.64	$182.65	$182.60
Purchase #3	$99.25	3.355%	$102.5798	$102.58	$102.60	$102.60
Purchase #4	$169.50	3.154%	$174.846	$174.85	$174.85	$174.80
Purchase #5	$160.45	5.395%	$169.1063	$169.11	$169.10	$169.10
Purchase #6	$134.86	5.300%	$142.0076	$142.01	$142.00	$142.00
Purchase #7	$149.73	9.830%	$164.4485	$164.45	$164.45	$164.40
7 purchase totals =	$988.91		$1,048.7547	$1,048.77	$1,048.80	$1,048.60