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	$96.53	13.473%	$109.5355	$109.54	$109.55	$109.50
Purchase #2	$136.44	5.867%	$144.4449	$144.44	$144.45	$144.40
Purchase #3	$150.51	5.159%	$158.2748	$158.27	$158.25	$158.30
Purchase #4	$201.92	8.607%	$219.2993	$219.30	$219.30	$219.30
Purchase #5	$38.25	8.392%	$41.4599	$41.46	$41.45	$41.50
Purchase #6	$149.30	10.661%	$165.2169	$165.22	$165.20	$165.20
Purchase #7	$157.36	4.519%	$164.4711	$164.47	$164.45	$164.50
7 purchase totals =	$930.31		$1,002.7024	$1,002.70	$1,002.65	$1,002.70