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	$177.29	7.219%	$190.0886	$190.09	$190.10	$190.10
Purchase #2	$89.57	13.561%	$101.7166	$101.72	$101.70	$101.70
Purchase #3	$139.92	6.619%	$149.1813	$149.18	$149.20	$149.20
Purchase #4	$105.57	3.274%	$109.0264	$109.03	$109.05	$109.00
Purchase #5	$134.30	6.492%	$143.0188	$143.02	$143.00	$143.00
Purchase #6	$196.45	9.613%	$215.3347	$215.33	$215.35	$215.30
Purchase #7	$202.73	3.813%	$210.4601	$210.46	$210.45	$210.50
7 purchase totals =	$1,045.83		$1,118.8265	$1,118.83	$1,118.85	$1,118.80