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	$59.90	3.648%	$62.0852	$62.09	$62.10	$62.10
Purchase #2	$163.55	6.753%	$174.5945	$174.59	$174.60	$174.60
Purchase #3	$209.35	9.364%	$228.9535	$228.95	$228.95	$229.00
Purchase #4	$52.86	13.232%	$59.8544	$59.85	$59.85	$59.90
Purchase #5	$29.72	13.750%	$33.8065	$33.81	$33.80	$33.80
Purchase #6	$72.49	13.429%	$82.2247	$82.22	$82.20	$82.20
Purchase #7	$135.57	10.566%	$149.8943	$149.89	$149.90	$149.90
7 purchase totals =	$723.44		$791.4131	$791.40	$791.40	$791.50