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	$53.56	5.496%	$56.5037	$56.50	$56.50	$56.50
Purchase #2	$153.79	4.207%	$160.2599	$160.26	$160.25	$160.30
Purchase #3	$77.38	4.425%	$80.8041	$80.80	$80.80	$80.80
Purchase #4	$146.52	6.703%	$156.3412	$156.34	$156.35	$156.30
Purchase #5	$248.28	6.243%	$263.7801	$263.78	$263.80	$263.80
Purchase #6	$229.76	10.377%	$253.6022	$253.60	$253.60	$253.60
Purchase #7	$179.84	9.324%	$196.6083	$196.61	$196.60	$196.60
7 purchase totals =	$1,089.13		$1,167.8995	$1,167.89	$1,167.90	$1,167.90