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	$118.40	8.543%	$128.5149	$128.51	$128.50	$128.50
Purchase #2	$36.57	3.276%	$37.768	$37.77	$37.75	$37.80
Purchase #3	$41.26	4.779%	$43.2318	$43.23	$43.25	$43.20
Purchase #4	$88.44	9.555%	$96.8904	$96.89	$96.90	$96.90
Purchase #5	$176.54	7.671%	$190.0824	$190.08	$190.10	$190.10
Purchase #6	$106.91	12.519%	$120.2941	$120.29	$120.30	$120.30
Purchase #7	$176.39	12.295%	$198.0772	$198.08	$198.10	$198.10
7 purchase totals =	$744.51		$814.8588	$814.85	$814.90	$814.90