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	$178.46	12.562%	$200.8781	$200.88	$200.90	$200.90
Purchase #2	$45.64	3.601%	$47.2835	$47.28	$47.30	$47.30
Purchase #3	$189.48	5.873%	$200.6082	$200.61	$200.60	$200.60
Purchase #4	$249.54	8.858%	$271.6443	$271.64	$271.65	$271.60
Purchase #5	$40.47	9.355%	$44.256	$44.26	$44.25	$44.30
Purchase #6	$42.41	4.365%	$44.2612	$44.26	$44.25	$44.30
Purchase #7	$193.40	8.787%	$210.3941	$210.39	$210.40	$210.40
7 purchase totals =	$939.40		$1,019.3254	$1,019.32	$1,019.35	$1,019.40