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	$223.48	9.672%	$245.095	$245.10	$245.10	$245.10
Purchase #2	$199.72	6.736%	$213.1731	$213.17	$213.15	$213.20
Purchase #3	$68.54	5.228%	$72.1233	$72.12	$72.10	$72.10
Purchase #4	$241.58	5.158%	$254.0407	$254.04	$254.05	$254.00
Purchase #5	$41.64	4.212%	$43.3939	$43.39	$43.40	$43.40
Purchase #6	$63.94	5.797%	$67.6466	$67.65	$67.65	$67.60
Purchase #7	$187.34	5.739%	$198.0914	$198.09	$198.10	$198.10
7 purchase totals =	$1,026.24		$1,093.5640	$1,093.56	$1,093.55	$1,093.50