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	$78.47	10.702%	$86.8679	$86.87	$86.85	$86.90
Purchase #2	$215.38	3.220%	$222.3152	$222.32	$222.30	$222.30
Purchase #3	$149.65	9.699%	$164.1646	$164.16	$164.15	$164.20
Purchase #4	$217.59	12.749%	$245.3305	$245.33	$245.35	$245.30
Purchase #5	$219.42	11.873%	$245.4717	$245.47	$245.45	$245.50
Purchase #6	$248.91	13.148%	$281.6367	$281.64	$281.65	$281.60
Purchase #7	$14.46	10.187%	$15.933	$15.93	$15.95	$15.90
7 purchase totals =	$1,143.88		$1,261.7196	$1,261.72	$1,261.70	$1,261.70