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	$48.71	9.350%	$53.2644	$53.26	$53.25	$53.30
Purchase #2	$233.83	3.467%	$241.9369	$241.94	$241.95	$241.90
Purchase #3	$118.28	12.683%	$133.2815	$133.28	$133.30	$133.30
Purchase #4	$89.37	7.491%	$96.0647	$96.06	$96.05	$96.10
Purchase #5	$245.50	12.518%	$276.2317	$276.23	$276.25	$276.20
Purchase #6	$161.31	11.539%	$179.9236	$179.92	$179.90	$179.90
Purchase #7	$76.30	7.662%	$82.1461	$82.15	$82.15	$82.10
7 purchase totals =	$973.30		$1,062.8489	$1,062.84	$1,062.85	$1,062.80