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	$180.32	7.870%	$194.5112	$194.51	$194.50	$194.50
Purchase #2	$158.92	6.376%	$169.0527	$169.05	$169.05	$169.10
Purchase #3	$55.69	3.355%	$57.5584	$57.56	$57.55	$57.60
Purchase #4	$19.27	6.831%	$20.5863	$20.59	$20.60	$20.60
Purchase #5	$174.91	13.468%	$198.4669	$198.47	$198.45	$198.50
Purchase #6	$181.58	3.361%	$187.6829	$187.68	$187.70	$187.70
Purchase #7	$237.73	5.774%	$251.4565	$251.46	$251.45	$251.50
7 purchase totals =	$1,008.42		$1,079.3149	$1,079.32	$1,079.30	$1,079.50