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	$156.89	7.117%	$168.0559	$168.06	$168.05	$168.10
Purchase #2	$56.85	8.407%	$61.6294	$61.63	$61.65	$61.60
Purchase #3	$30.37	5.488%	$32.0367	$32.04	$32.05	$32.00
Purchase #4	$21.89	7.712%	$23.5782	$23.58	$23.60	$23.60
Purchase #5	$247.85	3.457%	$256.4182	$256.42	$256.40	$256.40
Purchase #6	$168.37	10.103%	$185.3804	$185.38	$185.40	$185.40
Purchase #7	$162.74	11.354%	$181.2175	$181.22	$181.20	$181.20
7 purchase totals =	$844.96		$908.3163	$908.33	$908.35	$908.30