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	$39.68	11.506%	$44.2456	$44.25	$44.25	$44.20
Purchase #2	$89.69	5.278%	$94.4238	$94.42	$94.40	$94.40
Purchase #3	$129.71	5.648%	$137.036	$137.04	$137.05	$137.00
Purchase #4	$119.85	13.489%	$136.0166	$136.02	$136.00	$136.00
Purchase #5	$186.63	11.509%	$208.1092	$208.11	$208.10	$208.10
Purchase #6	$167.67	7.276%	$179.8697	$179.87	$179.85	$179.90
Purchase #7	$239.32	6.663%	$255.2659	$255.27	$255.25	$255.30
7 purchase totals =	$972.55		$1,054.9668	$1,054.98	$1,054.90	$1,054.90