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	$220.29	4.171%	$229.4783	$229.48	$229.50	$229.50
Purchase #2	$68.31	7.747%	$73.602	$73.60	$73.60	$73.60
Purchase #3	$6.92	3.672%	$7.1741	$7.17	$7.15	$7.20
Purchase #4	$73.41	12.450%	$82.5495	$82.55	$82.55	$82.50
Purchase #5	$219.43	9.199%	$239.6154	$239.62	$239.60	$239.60
Purchase #6	$227.80	7.763%	$245.4841	$245.48	$245.50	$245.50
Purchase #7	$215.46	5.499%	$227.3081	$227.31	$227.30	$227.30
7 purchase totals =	$1,031.62		$1,105.2115	$1,105.21	$1,105.20	$1,105.20