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	$70.29	3.136%	$72.4943	$72.49	$72.50	$72.50
Purchase #2	$206.84	5.309%	$217.8211	$217.82	$217.80	$217.80
Purchase #3	$157.77	9.215%	$172.3085	$172.31	$172.30	$172.30
Purchase #4	$245.62	3.678%	$254.6539	$254.65	$254.65	$254.70
Purchase #5	$114.79	5.210%	$120.7706	$120.77	$120.75	$120.80
Purchase #6	$60.64	5.553%	$64.0073	$64.01	$64.00	$64.00
Purchase #7	$118.36	7.755%	$127.5388	$127.54	$127.55	$127.50
7 purchase totals =	$974.31		$1,029.5945	$1,029.59	$1,029.55	$1,029.60