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	$154.87	3.200%	$159.8258	$159.83	$159.85	$159.80
Purchase #2	$207.37	4.337%	$216.3636	$216.36	$216.35	$216.40
Purchase #3	$212.51	7.708%	$228.8903	$228.89	$228.90	$228.90
Purchase #4	$56.93	13.476%	$64.6019	$64.60	$64.60	$64.60
Purchase #5	$95.46	9.850%	$104.8628	$104.86	$104.85	$104.90
Purchase #6	$178.75	9.255%	$195.2933	$195.29	$195.30	$195.30
Purchase #7	$80.56	12.804%	$90.8749	$90.87	$90.85	$90.90
7 purchase totals =	$986.45		$1,060.7126	$1,060.70	$1,060.70	$1,060.80