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	$94.87	10.696%	$105.0173	$105.02	$105.00	$105.00
Purchase #2	$155.30	7.236%	$166.5375	$166.54	$166.55	$166.50
Purchase #3	$192.80	10.229%	$212.5215	$212.52	$212.50	$212.50
Purchase #4	$34.39	8.121%	$37.1828	$37.18	$37.20	$37.20
Purchase #5	$207.42	7.643%	$223.2731	$223.27	$223.25	$223.30
Purchase #6	$102.36	3.351%	$105.7901	$105.79	$105.80	$105.80
Purchase #7	$191.99	12.426%	$215.8467	$215.85	$215.85	$215.80
7 purchase totals =	$979.13		$1,066.1690	$1,066.17	$1,066.15	$1,066.10