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	$126.26	3.793%	$131.049	$131.05	$131.05	$131.00
Purchase #2	$156.73	8.106%	$169.4345	$169.43	$169.45	$169.40
Purchase #3	$94.98	4.595%	$99.3443	$99.34	$99.35	$99.30
Purchase #4	$77.38	3.419%	$80.0256	$80.03	$80.05	$80.00
Purchase #5	$159.50	3.362%	$164.8624	$164.86	$164.85	$164.90
Purchase #6	$240.64	10.505%	$265.9192	$265.92	$265.90	$265.90
Purchase #7	$164.95	5.133%	$173.4169	$173.42	$173.40	$173.40
7 purchase totals =	$1,020.44		$1,084.0519	$1,084.05	$1,084.05	$1,083.90