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	$181.36	8.182%	$196.1989	$196.20	$196.20	$196.20
Purchase #2	$176.82	9.637%	$193.8601	$193.86	$193.85	$193.90
Purchase #3	$96.30	13.273%	$109.0819	$109.08	$109.10	$109.10
Purchase #4	$29.29	8.432%	$31.7597	$31.76	$31.75	$31.80
Purchase #5	$173.70	10.165%	$191.3566	$191.36	$191.35	$191.40
Purchase #6	$130.88	6.415%	$139.276	$139.28	$139.30	$139.30
Purchase #7	$92.39	7.351%	$99.1816	$99.18	$99.20	$99.20
7 purchase totals =	$880.74		$960.7148	$960.72	$960.75	$960.90