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	$164.27	12.747%	$185.2095	$185.21	$185.20	$185.20
Purchase #2	$107.92	4.686%	$112.9771	$112.98	$113.00	$113.00
Purchase #3	$185.70	5.642%	$196.1772	$196.18	$196.20	$196.20
Purchase #4	$150.79	3.772%	$156.4778	$156.48	$156.50	$156.50
Purchase #5	$109.48	5.147%	$115.1149	$115.11	$115.10	$115.10
Purchase #6	$51.50	5.870%	$54.5231	$54.52	$54.50	$54.50
Purchase #7	$180.53	4.474%	$188.6069	$188.61	$188.60	$188.60
7 purchase totals =	$950.19		$1,009.0865	$1,009.09	$1,009.10	$1,009.10