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	$241.31	11.765%	$269.7001	$269.70	$269.70	$269.70
Purchase #2	$187.87	5.558%	$198.3118	$198.31	$198.30	$198.30
Purchase #3	$113.25	3.701%	$117.4414	$117.44	$117.45	$117.40
Purchase #4	$142.40	13.816%	$162.074	$162.07	$162.05	$162.10
Purchase #5	$82.41	3.557%	$85.3413	$85.34	$85.35	$85.30
Purchase #6	$248.86	3.725%	$258.13	$258.13	$258.15	$258.10
Purchase #7	$86.63	4.269%	$90.3282	$90.33	$90.35	$90.30
7 purchase totals =	$1,102.73		$1,181.3268	$1,181.32	$1,181.35	$1,181.20