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	$166.76	8.846%	$181.5116	$181.51	$181.50	$181.50
Purchase #2	$168.72	4.597%	$176.4761	$176.48	$176.50	$176.50
Purchase #3	$206.56	10.855%	$228.9821	$228.98	$229.00	$229.00
Purchase #4	$28.56	10.668%	$31.6068	$31.61	$31.60	$31.60
Purchase #5	$89.43	12.824%	$100.8985	$100.90	$100.90	$100.90
Purchase #6	$209.64	10.290%	$231.212	$231.21	$231.20	$231.20
Purchase #7	$218.27	10.497%	$241.1818	$241.18	$241.20	$241.20
7 purchase totals =	$1,087.94		$1,191.8689	$1,191.87	$1,191.90	$1,191.90