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	$174.33	9.287%	$190.52	$190.52	$190.50	$190.50
Purchase #2	$191.75	6.183%	$203.6059	$203.61	$203.60	$203.60
Purchase #3	$118.59	6.339%	$126.1074	$126.11	$126.10	$126.10
Purchase #4	$162.30	3.551%	$168.0633	$168.06	$168.05	$168.10
Purchase #5	$91.30	9.254%	$99.7489	$99.75	$99.75	$99.70
Purchase #6	$240.65	13.660%	$273.5228	$273.52	$273.50	$273.50
Purchase #7	$52.40	10.817%	$58.0681	$58.07	$58.05	$58.10
7 purchase totals =	$1,031.32		$1,119.6364	$1,119.64	$1,119.55	$1,119.60