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	$192.26	3.150%	$198.3162	$198.32	$198.30	$198.30
Purchase #2	$30.41	6.303%	$32.3267	$32.33	$32.35	$32.30
Purchase #3	$20.33	5.482%	$21.4445	$21.44	$21.45	$21.40
Purchase #4	$5.34	5.842%	$5.652	$5.65	$5.65	$5.70
Purchase #5	$196.52	8.156%	$212.5482	$212.55	$212.55	$212.50
Purchase #6	$149.28	10.200%	$164.5066	$164.51	$164.50	$164.50
Purchase #7	$114.94	7.712%	$123.8042	$123.80	$123.80	$123.80
7 purchase totals =	$709.08		$758.5984	$758.60	$758.60	$758.50