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	$150.32	11.150%	$167.0807	$167.08	$167.10	$167.10
Purchase #2	$89.27	6.571%	$95.1359	$95.14	$95.15	$95.10
Purchase #3	$95.82	4.314%	$99.9537	$99.95	$99.95	$100.00
Purchase #4	$17.66	13.270%	$20.0035	$20.00	$20.00	$20.00
Purchase #5	$177.90	10.419%	$196.4354	$196.44	$196.45	$196.40
Purchase #6	$149.73	13.350%	$169.719	$169.72	$169.70	$169.70
Purchase #7	$229.83	9.535%	$251.7443	$251.74	$251.75	$251.70
7 purchase totals =	$910.53		$1,000.0725	$1,000.07	$1,000.10	$1,000.00