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	$174.59	5.702%	$184.5451	$184.55	$184.55	$184.50
Purchase #2	$249.70	13.172%	$282.5905	$282.59	$282.60	$282.60
Purchase #3	$200.69	6.822%	$214.3811	$214.38	$214.40	$214.40
Purchase #4	$12.25	7.377%	$13.1537	$13.15	$13.15	$13.20
Purchase #5	$211.76	11.148%	$235.367	$235.37	$235.35	$235.40
Purchase #6	$201.50	10.608%	$222.8751	$222.88	$222.90	$222.90
Purchase #7	$96.60	10.222%	$106.4745	$106.47	$106.45	$106.50
7 purchase totals =	$1,147.09		$1,259.3870	$1,259.39	$1,259.40	$1,259.50