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	$175.84	6.587%	$187.4226	$187.42	$187.40	$187.40
Purchase #2	$191.29	4.652%	$200.1888	$200.19	$200.20	$200.20
Purchase #3	$166.86	4.834%	$174.926	$174.93	$174.95	$174.90
Purchase #4	$6.78	13.652%	$7.7056	$7.71	$7.70	$7.70
Purchase #5	$35.34	6.799%	$37.7428	$37.74	$37.75	$37.70
Purchase #6	$80.93	13.109%	$91.5391	$91.54	$91.55	$91.50
Purchase #7	$31.67	6.616%	$33.7653	$33.77	$33.75	$33.80
7 purchase totals =	$688.71		$733.2902	$733.30	$733.30	$733.20