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	$199.70	5.441%	$210.5657	$210.57	$210.55	$210.60
Purchase #2	$112.56	13.631%	$127.9031	$127.90	$127.90	$127.90
Purchase #3	$247.33	12.829%	$279.06	$279.06	$279.05	$279.10
Purchase #4	$56.54	9.553%	$61.9413	$61.94	$61.95	$61.90
Purchase #5	$115.92	10.315%	$127.8771	$127.88	$127.90	$127.90
Purchase #6	$145.33	5.366%	$153.1284	$153.13	$153.15	$153.10
Purchase #7	$97.37	9.448%	$106.5695	$106.57	$106.55	$106.60
7 purchase totals =	$974.75		$1,067.0451	$1,067.05	$1,067.05	$1,067.10