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	$147.56	4.502%	$154.2032	$154.20	$154.20	$154.20
Purchase #2	$136.68	5.515%	$144.2179	$144.22	$144.20	$144.20
Purchase #3	$245.57	13.673%	$279.1468	$279.15	$279.15	$279.10
Purchase #4	$95.59	6.792%	$102.0825	$102.08	$102.10	$102.10
Purchase #5	$72.58	13.392%	$82.2999	$82.30	$82.30	$82.30
Purchase #6	$176.28	5.687%	$186.305	$186.31	$186.30	$186.30
Purchase #7	$60.53	12.118%	$67.865	$67.87	$67.85	$67.90
7 purchase totals =	$934.79		$1,016.1203	$1,016.13	$1,016.10	$1,016.10