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	$223.44	4.764%	$234.0847	$234.08	$234.10	$234.10
Purchase #2	$73.72	6.461%	$78.483	$78.48	$78.50	$78.50
Purchase #3	$7.89	7.620%	$8.4912	$8.49	$8.50	$8.50
Purchase #4	$91.38	5.557%	$96.458	$96.46	$96.45	$96.50
Purchase #5	$72.54	13.287%	$82.1784	$82.18	$82.20	$82.20
Purchase #6	$151.69	8.243%	$164.1938	$164.19	$164.20	$164.20
Purchase #7	$204.99	7.801%	$220.9813	$220.98	$221.00	$221.00
7 purchase totals =	$825.65		$884.8704	$884.86	$884.95	$885.00