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	$108.56	5.527%	$114.5601	$114.56	$114.55	$114.60
Purchase #2	$55.34	12.141%	$62.0588	$62.06	$62.05	$62.10
Purchase #3	$40.56	11.277%	$45.134	$45.13	$45.15	$45.10
Purchase #4	$191.38	10.228%	$210.9543	$210.95	$210.95	$211.00
Purchase #5	$145.35	10.456%	$160.5478	$160.55	$160.55	$160.50
Purchase #6	$147.98	12.744%	$166.8386	$166.84	$166.85	$166.80
Purchase #7	$233.28	7.388%	$250.5147	$250.51	$250.50	$250.50
7 purchase totals =	$922.45		$1,010.6083	$1,010.60	$1,010.60	$1,010.60