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	$48.64	13.685%	$55.2964	$55.30	$55.30	$55.30
Purchase #2	$250.52	9.228%	$273.638	$273.64	$273.65	$273.60
Purchase #3	$174.75	7.815%	$188.4067	$188.41	$188.40	$188.40
Purchase #4	$119.54	13.592%	$135.7879	$135.79	$135.80	$135.80
Purchase #5	$155.64	4.439%	$162.5489	$162.55	$162.55	$162.50
Purchase #6	$136.26	5.862%	$144.2476	$144.25	$144.25	$144.20
Purchase #7	$182.35	4.448%	$190.4609	$190.46	$190.45	$190.50
7 purchase totals =	$1,067.70		$1,150.3864	$1,150.40	$1,150.40	$1,150.30