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	$45.49	10.411%	$50.226	$50.23	$50.25	$50.20
Purchase #2	$181.55	7.642%	$195.4241	$195.42	$195.40	$195.40
Purchase #3	$237.94	12.688%	$268.1298	$268.13	$268.15	$268.10
Purchase #4	$40.60	10.592%	$44.9004	$44.90	$44.90	$44.90
Purchase #5	$72.85	8.188%	$78.815	$78.82	$78.80	$78.80
Purchase #6	$139.35	9.104%	$152.0364	$152.04	$152.05	$152.00
Purchase #7	$205.39	10.607%	$227.1757	$227.18	$227.20	$227.20
7 purchase totals =	$923.17		$1,016.7074	$1,016.72	$1,016.75	$1,016.60