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	$130.66	13.852%	$148.759	$148.76	$148.75	$148.80
Purchase #2	$149.99	6.290%	$159.4244	$159.42	$159.40	$159.40
Purchase #3	$121.60	5.113%	$127.8174	$127.82	$127.80	$127.80
Purchase #4	$154.67	6.326%	$164.4544	$164.45	$164.45	$164.50
Purchase #5	$122.85	3.834%	$127.5601	$127.56	$127.55	$127.60
Purchase #6	$118.92	4.609%	$124.401	$124.40	$124.40	$124.40
Purchase #7	$181.57	3.497%	$187.9195	$187.92	$187.90	$187.90
7 purchase totals =	$980.26		$1,040.3358	$1,040.33	$1,040.25	$1,040.40