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	$139.42	9.725%	$152.9786	$152.98	$153.00	$153.00
Purchase #2	$219.46	4.680%	$229.7307	$229.73	$229.75	$229.70
Purchase #3	$173.77	4.870%	$182.2326	$182.23	$182.25	$182.20
Purchase #4	$98.92	12.445%	$111.2306	$111.23	$111.25	$111.20
Purchase #5	$228.39	6.440%	$243.0983	$243.10	$243.10	$243.10
Purchase #6	$75.47	8.869%	$82.1634	$82.16	$82.15	$82.20
Purchase #7	$114.70	7.393%	$123.1798	$123.18	$123.20	$123.20
7 purchase totals =	$1,050.13		$1,124.6140	$1,124.61	$1,124.70	$1,124.60