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	$229.78	7.382%	$246.7424	$246.74	$246.75	$246.70
Purchase #2	$142.38	3.847%	$147.8574	$147.86	$147.85	$147.90
Purchase #3	$93.38	3.636%	$96.7753	$96.78	$96.80	$96.80
Purchase #4	$106.57	4.419%	$111.2793	$111.28	$111.30	$111.30
Purchase #5	$237.37	10.335%	$261.9022	$261.90	$261.90	$261.90
Purchase #6	$43.35	7.361%	$46.541	$46.54	$46.55	$46.50
Purchase #7	$209.95	4.454%	$219.3012	$219.30	$219.30	$219.30
7 purchase totals =	$1,062.78		$1,130.3988	$1,130.40	$1,130.45	$1,130.40