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	$240.90	5.642%	$254.4916	$254.49	$254.50	$254.50
Purchase #2	$48.26	5.809%	$51.0634	$51.06	$51.05	$51.10
Purchase #3	$146.36	13.769%	$166.5123	$166.51	$166.50	$166.50
Purchase #4	$220.69	5.856%	$233.6136	$233.61	$233.60	$233.60
Purchase #5	$106.60	7.241%	$114.3189	$114.32	$114.30	$114.30
Purchase #6	$118.40	10.378%	$130.6876	$130.69	$130.70	$130.70
Purchase #7	$136.25	10.490%	$150.5426	$150.54	$150.55	$150.50
7 purchase totals =	$1,017.46		$1,101.2300	$1,101.22	$1,101.20	$1,101.20