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	$150.72	12.700%	$169.8614	$169.86	$169.85	$169.90
Purchase #2	$239.77	3.556%	$248.2962	$248.30	$248.30	$248.30
Purchase #3	$9.64	13.293%	$10.9214	$10.92	$10.90	$10.90
Purchase #4	$137.52	3.421%	$142.2246	$142.22	$142.20	$142.20
Purchase #5	$94.82	7.413%	$101.849	$101.85	$101.85	$101.80
Purchase #6	$170.55	10.663%	$188.7357	$188.74	$188.75	$188.70
Purchase #7	$131.98	7.820%	$142.3008	$142.30	$142.30	$142.30
7 purchase totals =	$935.00		$1,004.1891	$1,004.19	$1,004.15	$1,004.10