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	$12.65	13.196%	$14.3193	$14.32	$14.30	$14.30
Purchase #2	$147.86	4.871%	$155.0623	$155.06	$155.05	$155.10
Purchase #3	$89.88	9.599%	$98.5076	$98.51	$98.50	$98.50
Purchase #4	$205.62	8.826%	$223.768	$223.77	$223.75	$223.80
Purchase #5	$180.69	4.194%	$188.2681	$188.27	$188.25	$188.30
Purchase #6	$137.25	13.709%	$156.0656	$156.07	$156.05	$156.10
Purchase #7	$68.83	5.755%	$72.7912	$72.79	$72.80	$72.80
7 purchase totals =	$842.78		$908.7821	$908.79	$908.70	$908.90