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	$51.27	4.389%	$53.5202	$53.52	$53.50	$53.50
Purchase #2	$156.51	7.348%	$168.0104	$168.01	$168.00	$168.00
Purchase #3	$168.88	7.439%	$181.443	$181.44	$181.45	$181.40
Purchase #4	$96.41	4.218%	$100.4766	$100.48	$100.50	$100.50
Purchase #5	$159.78	7.165%	$171.2282	$171.23	$171.25	$171.20
Purchase #6	$190.33	6.278%	$202.2789	$202.28	$202.30	$202.30
Purchase #7	$118.65	4.133%	$123.5538	$123.55	$123.55	$123.60
7 purchase totals =	$941.83		$1,000.5111	$1,000.51	$1,000.55	$1,000.50