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	$204.44	10.632%	$226.1761	$226.18	$226.20	$226.20
Purchase #2	$201.82	10.771%	$223.558	$223.56	$223.55	$223.60
Purchase #3	$20.52	6.415%	$21.8364	$21.84	$21.85	$21.80
Purchase #4	$118.66	4.400%	$123.881	$123.88	$123.90	$123.90
Purchase #5	$195.59	3.309%	$202.0621	$202.06	$202.05	$202.10
Purchase #6	$52.31	11.140%	$58.1373	$58.14	$58.15	$58.10
Purchase #7	$142.77	6.794%	$152.4698	$152.47	$152.45	$152.50
7 purchase totals =	$936.11		$1,008.1207	$1,008.13	$1,008.15	$1,008.20