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	$185.94	11.560%	$207.4347	$207.43	$207.45	$207.40
Purchase #2	$47.40	3.169%	$48.9021	$48.90	$48.90	$48.90
Purchase #3	$72.44	13.352%	$82.1122	$82.11	$82.10	$82.10
Purchase #4	$227.48	11.371%	$253.3468	$253.35	$253.35	$253.30
Purchase #5	$212.87	6.555%	$226.8236	$226.82	$226.80	$226.80
Purchase #6	$185.89	4.802%	$194.8164	$194.82	$194.80	$194.80
Purchase #7	$73.32	13.108%	$82.9308	$82.93	$82.95	$82.90
7 purchase totals =	$1,005.34		$1,096.3666	$1,096.36	$1,096.35	$1,096.20