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	$215.46	6.625%	$229.7342	$229.73	$229.75	$229.70
Purchase #2	$33.88	11.851%	$37.8951	$37.90	$37.90	$37.90
Purchase #3	$18.90	13.617%	$21.4736	$21.47	$21.45	$21.50
Purchase #4	$176.91	4.721%	$185.2619	$185.26	$185.25	$185.30
Purchase #5	$166.32	5.477%	$175.4293	$175.43	$175.45	$175.40
Purchase #6	$73.76	6.254%	$78.373	$78.37	$78.35	$78.40
Purchase #7	$166.42	4.732%	$174.295	$174.30	$174.30	$174.30
7 purchase totals =	$851.65		$902.4621	$902.46	$902.45	$902.50