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	$50.76	8.160%	$54.902	$54.90	$54.90	$54.90
Purchase #2	$201.68	10.489%	$222.8342	$222.83	$222.85	$222.80
Purchase #3	$96.46	12.701%	$108.7114	$108.71	$108.70	$108.70
Purchase #4	$224.72	6.280%	$238.8324	$238.83	$238.85	$238.80
Purchase #5	$94.94	5.699%	$100.3506	$100.35	$100.35	$100.40
Purchase #6	$240.61	11.689%	$268.7349	$268.73	$268.75	$268.70
Purchase #7	$22.55	4.160%	$23.4881	$23.49	$23.50	$23.50
7 purchase totals =	$931.72		$1,017.8536	$1,017.84	$1,017.90	$1,017.80