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	$148.82	3.409%	$153.8933	$153.89	$153.90	$153.90
Purchase #2	$99.69	11.728%	$111.3816	$111.38	$111.40	$111.40
Purchase #3	$175.53	12.764%	$197.9346	$197.93	$197.95	$197.90
Purchase #4	$195.86	10.276%	$215.9866	$215.99	$216.00	$216.00
Purchase #5	$134.42	7.822%	$144.9343	$144.93	$144.95	$144.90
Purchase #6	$229.68	7.647%	$247.2436	$247.24	$247.25	$247.20
Purchase #7	$89.28	12.740%	$100.6543	$100.65	$100.65	$100.70
7 purchase totals =	$1,073.28		$1,172.0283	$1,172.01	$1,172.10	$1,172.00