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	$215.93	8.321%	$233.8975	$233.90	$233.90	$233.90
Purchase #2	$36.86	12.242%	$41.3724	$41.37	$41.35	$41.40
Purchase #3	$178.76	3.426%	$184.8843	$184.88	$184.90	$184.90
Purchase #4	$50.76	10.280%	$55.9781	$55.98	$56.00	$56.00
Purchase #5	$168.84	6.112%	$179.1595	$179.16	$179.15	$179.20
Purchase #6	$170.62	10.707%	$188.8883	$188.89	$188.90	$188.90
Purchase #7	$72.87	8.255%	$78.8854	$78.89	$78.90	$78.90
7 purchase totals =	$894.64		$963.0655	$963.07	$963.10	$963.20