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	$156.33	3.768%	$162.2205	$162.22	$162.20	$162.20
Purchase #2	$88.69	13.111%	$100.3181	$100.32	$100.30	$100.30
Purchase #3	$91.63	9.641%	$100.464	$100.46	$100.45	$100.50
Purchase #4	$41.42	7.166%	$44.3882	$44.39	$44.40	$44.40
Purchase #5	$129.40	8.321%	$140.1674	$140.17	$140.15	$140.20
Purchase #6	$104.38	9.393%	$114.1844	$114.18	$114.20	$114.20
Purchase #7	$61.54	11.864%	$68.8411	$68.84	$68.85	$68.80
7 purchase totals =	$673.39		$730.5837	$730.58	$730.55	$730.60