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	$250.38	7.753%	$269.792	$269.79	$269.80	$269.80
Purchase #2	$40.38	5.871%	$42.7507	$42.75	$42.75	$42.80
Purchase #3	$175.85	11.618%	$196.2803	$196.28	$196.30	$196.30
Purchase #4	$162.63	6.556%	$173.292	$173.29	$173.30	$173.30
Purchase #5	$145.91	9.116%	$159.2112	$159.21	$159.20	$159.20
Purchase #6	$213.84	6.542%	$227.8294	$227.83	$227.85	$227.80
Purchase #7	$27.69	12.474%	$31.1441	$31.14	$31.15	$31.10
7 purchase totals =	$1,016.68		$1,100.2997	$1,100.29	$1,100.35	$1,100.30