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	$205.70	9.630%	$225.5089	$225.51	$225.50	$225.50
Purchase #2	$156.86	7.346%	$168.3829	$168.38	$168.40	$168.40
Purchase #3	$39.71	9.235%	$43.3772	$43.38	$43.40	$43.40
Purchase #4	$149.62	7.254%	$160.4734	$160.47	$160.45	$160.50
Purchase #5	$180.61	4.525%	$188.7826	$188.78	$188.80	$188.80
Purchase #6	$35.63	4.480%	$37.2262	$37.23	$37.25	$37.20
Purchase #7	$126.56	10.375%	$139.6906	$139.69	$139.70	$139.70
7 purchase totals =	$894.69		$963.4418	$963.44	$963.50	$963.50