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	$178.86	6.841%	$191.0958	$191.10	$191.10	$191.10
Purchase #2	$101.68	8.113%	$109.9293	$109.93	$109.95	$109.90
Purchase #3	$25.86	10.229%	$28.5052	$28.51	$28.50	$28.50
Purchase #4	$53.36	3.430%	$55.1902	$55.19	$55.20	$55.20
Purchase #5	$65.37	11.611%	$72.9601	$72.96	$72.95	$73.00
Purchase #6	$38.71	6.479%	$41.218	$41.22	$41.20	$41.20
Purchase #7	$208.67	11.117%	$231.8678	$231.87	$231.85	$231.90
7 purchase totals =	$672.51		$730.7664	$730.78	$730.75	$730.80