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	$85.48	4.244%	$89.1078	$89.11	$89.10	$89.10
Purchase #2	$96.69	3.456%	$100.0316	$100.03	$100.05	$100.00
Purchase #3	$92.35	10.748%	$102.2758	$102.28	$102.30	$102.30
Purchase #4	$20.88	4.490%	$21.8175	$21.82	$21.80	$21.80
Purchase #5	$209.86	9.347%	$229.4756	$229.48	$229.50	$229.50
Purchase #6	$92.56	12.836%	$104.441	$104.44	$104.45	$104.40
Purchase #7	$80.41	4.502%	$84.0301	$84.03	$84.05	$84.00
7 purchase totals =	$678.23		$731.1794	$731.19	$731.25	$731.10