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	$140.34	5.149%	$147.5661	$147.57	$147.55	$147.60
Purchase #2	$240.97	6.354%	$256.2812	$256.28	$256.30	$256.30
Purchase #3	$51.38	7.825%	$55.4005	$55.40	$55.40	$55.40
Purchase #4	$196.79	4.316%	$205.2835	$205.28	$205.30	$205.30
Purchase #5	$93.28	5.663%	$98.5624	$98.56	$98.55	$98.60
Purchase #6	$174.49	9.409%	$190.9078	$190.91	$190.90	$190.90
Purchase #7	$111.33	7.612%	$119.8044	$119.80	$119.80	$119.80
7 purchase totals =	$1,008.58		$1,073.8059	$1,073.80	$1,073.80	$1,073.90