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	$139.65	11.484%	$155.6874	$155.69	$155.70	$155.70
Purchase #2	$153.86	13.618%	$174.8127	$174.81	$174.80	$174.80
Purchase #3	$73.27	12.831%	$82.6713	$82.67	$82.65	$82.70
Purchase #4	$73.59	6.472%	$78.3527	$78.35	$78.35	$78.40
Purchase #5	$56.48	12.126%	$63.3288	$63.33	$63.35	$63.30
Purchase #6	$172.50	12.125%	$193.4156	$193.42	$193.40	$193.40
Purchase #7	$242.82	7.607%	$261.2913	$261.29	$261.30	$261.30
7 purchase totals =	$912.17		$1,009.5598	$1,009.56	$1,009.55	$1,009.60