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	$60.46	4.582%	$63.2303	$63.23	$63.25	$63.20
Purchase #2	$43.62	7.550%	$46.9133	$46.91	$46.90	$46.90
Purchase #3	$84.84	6.303%	$90.1875	$90.19	$90.20	$90.20
Purchase #4	$99.57	4.118%	$103.6703	$103.67	$103.65	$103.70
Purchase #5	$155.53	4.466%	$162.476	$162.48	$162.50	$162.50
Purchase #6	$142.27	9.806%	$156.221	$156.22	$156.20	$156.20
Purchase #7	$135.94	8.686%	$147.7477	$147.75	$147.75	$147.70
7 purchase totals =	$722.23		$770.4461	$770.45	$770.45	$770.40