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	$171.54	10.801%	$190.068	$190.07	$190.05	$190.10
Purchase #2	$76.38	5.183%	$80.3388	$80.34	$80.35	$80.30
Purchase #3	$57.39	8.700%	$62.3829	$62.38	$62.40	$62.40
Purchase #4	$171.79	10.203%	$189.3177	$189.32	$189.30	$189.30
Purchase #5	$162.99	7.657%	$175.4701	$175.47	$175.45	$175.50
Purchase #6	$35.33	12.554%	$39.7653	$39.77	$39.75	$39.80
Purchase #7	$144.54	13.818%	$164.5125	$164.51	$164.50	$164.50
7 purchase totals =	$819.96		$901.8553	$901.86	$901.80	$901.90