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	$89.69	3.532%	$92.8579	$92.86	$92.85	$92.90
Purchase #2	$41.69	5.358%	$43.9238	$43.92	$43.90	$43.90
Purchase #3	$227.28	3.354%	$234.903	$234.90	$234.90	$234.90
Purchase #4	$209.80	12.169%	$235.3306	$235.33	$235.35	$235.30
Purchase #5	$47.52	9.545%	$52.0558	$52.06	$52.05	$52.10
Purchase #6	$114.65	11.387%	$127.7052	$127.71	$127.70	$127.70
Purchase #7	$56.29	9.326%	$61.5396	$61.54	$61.55	$61.50
7 purchase totals =	$786.92		$848.3159	$848.32	$848.30	$848.30