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	$14.93	3.464%	$15.4472	$15.45	$15.45	$15.40
Purchase #2	$42.63	5.830%	$45.1153	$45.12	$45.10	$45.10
Purchase #3	$5.99	13.443%	$6.7952	$6.80	$6.80	$6.80
Purchase #4	$236.60	9.342%	$258.7032	$258.70	$258.70	$258.70
Purchase #5	$185.52	7.871%	$200.1223	$200.12	$200.10	$200.10
Purchase #6	$186.31	12.471%	$209.5447	$209.54	$209.55	$209.50
Purchase #7	$243.88	9.280%	$266.5121	$266.51	$266.50	$266.50
7 purchase totals =	$915.86		$1,002.2400	$1,002.24	$1,002.20	$1,002.10