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	$100.25	5.541%	$105.8049	$105.80	$105.80	$105.80
Purchase #2	$50.77	3.552%	$52.5734	$52.57	$52.55	$52.60
Purchase #3	$99.99	3.395%	$103.3847	$103.38	$103.40	$103.40
Purchase #4	$102.73	5.788%	$108.676	$108.68	$108.70	$108.70
Purchase #5	$191.94	6.870%	$205.1263	$205.13	$205.15	$205.10
Purchase #6	$249.46	10.458%	$275.5485	$275.55	$275.55	$275.50
Purchase #7	$175.74	3.410%	$181.7327	$181.73	$181.75	$181.70
7 purchase totals =	$970.88		$1,032.8465	$1,032.84	$1,032.90	$1,032.80