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	$171.72	8.275%	$185.9298	$185.93	$185.95	$185.90
Purchase #2	$179.54	11.515%	$200.214	$200.21	$200.20	$200.20
Purchase #3	$190.49	5.281%	$200.5498	$200.55	$200.55	$200.50
Purchase #4	$111.39	5.454%	$117.4652	$117.47	$117.45	$117.50
Purchase #5	$159.98	4.510%	$167.1951	$167.20	$167.20	$167.20
Purchase #6	$98.53	12.142%	$110.4935	$110.49	$110.50	$110.50
Purchase #7	$116.71	5.758%	$123.4302	$123.43	$123.45	$123.40
7 purchase totals =	$1,028.36		$1,105.2776	$1,105.28	$1,105.30	$1,105.20