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	$91.49	5.367%	$96.4003	$96.40	$96.40	$96.40
Purchase #2	$123.36	6.825%	$131.7793	$131.78	$131.80	$131.80
Purchase #3	$166.31	7.465%	$178.725	$178.73	$178.75	$178.70
Purchase #4	$103.85	10.322%	$114.5694	$114.57	$114.55	$114.60
Purchase #5	$45.93	9.527%	$50.3058	$50.31	$50.30	$50.30
Purchase #6	$131.25	7.322%	$140.8601	$140.86	$140.85	$140.90
Purchase #7	$91.27	7.437%	$98.0577	$98.06	$98.05	$98.10
7 purchase totals =	$753.46		$810.6976	$810.71	$810.70	$810.80