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	$78.83	4.542%	$82.4105	$82.41	$82.40	$82.40
Purchase #2	$170.25	4.750%	$178.3369	$178.34	$178.35	$178.30
Purchase #3	$55.67	10.777%	$61.6696	$61.67	$61.65	$61.70
Purchase #4	$161.96	3.148%	$167.0585	$167.06	$167.05	$167.10
Purchase #5	$88.79	12.159%	$99.586	$99.59	$99.60	$99.60
Purchase #6	$177.43	6.830%	$189.5485	$189.55	$189.55	$189.50
Purchase #7	$13.56	4.299%	$14.1429	$14.14	$14.15	$14.10
7 purchase totals =	$746.49		$792.7529	$792.76	$792.75	$792.70