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	$93.32	7.612%	$100.4235	$100.42	$100.40	$100.40
Purchase #2	$64.77	11.506%	$72.2224	$72.22	$72.20	$72.20
Purchase #3	$173.99	6.372%	$185.0766	$185.08	$185.10	$185.10
Purchase #4	$194.85	4.834%	$204.269	$204.27	$204.25	$204.30
Purchase #5	$101.62	8.184%	$109.9366	$109.94	$109.95	$109.90
Purchase #6	$223.49	11.183%	$248.4829	$248.48	$248.50	$248.50
Purchase #7	$86.90	5.354%	$91.5526	$91.55	$91.55	$91.60
7 purchase totals =	$938.94		$1,011.9636	$1,011.96	$1,011.95	$1,012.00