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	$130.81	10.231%	$144.1932	$144.19	$144.20	$144.20
Purchase #2	$140.54	11.464%	$156.6515	$156.65	$156.65	$156.70
Purchase #3	$86.64	6.551%	$92.3158	$92.32	$92.30	$92.30
Purchase #4	$81.28	9.571%	$89.0593	$89.06	$89.05	$89.10
Purchase #5	$247.29	10.474%	$273.1912	$273.19	$273.20	$273.20
Purchase #6	$14.78	6.748%	$15.7774	$15.78	$15.80	$15.80
Purchase #7	$28.52	10.710%	$31.5745	$31.57	$31.55	$31.60
7 purchase totals =	$729.86		$802.7629	$802.76	$802.75	$802.90