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	$144.40	7.544%	$155.2935	$155.29	$155.30	$155.30
Purchase #2	$86.41	3.229%	$89.2002	$89.20	$89.20	$89.20
Purchase #3	$154.43	8.706%	$167.8747	$167.87	$167.85	$167.90
Purchase #4	$141.64	8.236%	$153.3055	$153.31	$153.30	$153.30
Purchase #5	$17.58	13.107%	$19.8842	$19.88	$19.90	$19.90
Purchase #6	$175.60	5.297%	$184.9015	$184.90	$184.90	$184.90
Purchase #7	$151.50	13.427%	$171.8419	$171.84	$171.85	$171.80
7 purchase totals =	$871.56		$942.3015	$942.29	$942.30	$942.30