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	$173.76	13.173%	$196.6494	$196.65	$196.65	$196.60
Purchase #2	$237.96	6.871%	$254.3102	$254.31	$254.30	$254.30
Purchase #3	$63.92	7.328%	$68.6041	$68.60	$68.60	$68.60
Purchase #4	$93.76	6.146%	$99.5225	$99.52	$99.50	$99.50
Purchase #5	$180.37	6.859%	$192.7416	$192.74	$192.75	$192.70
Purchase #6	$72.60	10.530%	$80.2448	$80.24	$80.25	$80.20
Purchase #7	$227.94	9.314%	$249.1703	$249.17	$249.15	$249.20
7 purchase totals =	$1,050.31		$1,141.2429	$1,141.23	$1,141.20	$1,141.10