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	$58.74	6.436%	$62.5205	$62.52	$62.50	$62.50
Purchase #2	$160.69	12.286%	$180.4324	$180.43	$180.45	$180.40
Purchase #3	$21.49	13.220%	$24.331	$24.33	$24.35	$24.30
Purchase #4	$218.40	11.328%	$243.1404	$243.14	$243.15	$243.10
Purchase #5	$43.53	13.802%	$49.538	$49.54	$49.55	$49.50
Purchase #6	$243.94	6.535%	$259.8815	$259.88	$259.90	$259.90
Purchase #7	$196.73	7.260%	$211.0126	$211.01	$211.00	$211.00
7 purchase totals =	$943.52		$1,030.8564	$1,030.85	$1,030.90	$1,030.70