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	$198.77	6.398%	$211.4873	$211.49	$211.50	$211.50
Purchase #2	$113.55	8.543%	$123.2506	$123.25	$123.25	$123.30
Purchase #3	$127.31	10.625%	$140.8367	$140.84	$140.85	$140.80
Purchase #4	$16.63	9.375%	$18.1891	$18.19	$18.20	$18.20
Purchase #5	$182.70	7.729%	$196.8209	$196.82	$196.80	$196.80
Purchase #6	$156.42	5.524%	$165.0606	$165.06	$165.05	$165.10
Purchase #7	$236.80	8.336%	$256.5396	$256.54	$256.55	$256.50
7 purchase totals =	$1,032.18		$1,112.1848	$1,112.19	$1,112.20	$1,112.20