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	$65.64	9.282%	$71.7327	$71.73	$71.75	$71.70
Purchase #2	$185.31	5.238%	$195.0165	$195.02	$195.00	$195.00
Purchase #3	$183.88	12.282%	$206.4641	$206.46	$206.45	$206.50
Purchase #4	$138.32	3.116%	$142.6301	$142.63	$142.65	$142.60
Purchase #5	$175.60	7.303%	$188.4241	$188.42	$188.40	$188.40
Purchase #6	$59.37	4.673%	$62.1444	$62.14	$62.15	$62.10
Purchase #7	$129.33	10.502%	$142.9122	$142.91	$142.90	$142.90
7 purchase totals =	$937.45		$1,009.3241	$1,009.31	$1,009.30	$1,009.20