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	$146.28	13.228%	$165.6299	$165.63	$165.65	$165.60
Purchase #2	$112.98	13.334%	$128.0448	$128.04	$128.05	$128.00
Purchase #3	$171.47	4.795%	$179.692	$179.69	$179.70	$179.70
Purchase #4	$35.83	6.214%	$38.0565	$38.06	$38.05	$38.10
Purchase #5	$128.78	11.281%	$143.3077	$143.31	$143.30	$143.30
Purchase #6	$57.46	8.443%	$62.3113	$62.31	$62.30	$62.30
Purchase #7	$192.48	11.199%	$214.0358	$214.04	$214.05	$214.00
7 purchase totals =	$845.28		$931.0780	$931.08	$931.10	$931.00