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	$40.35	4.658%	$42.2295	$42.23	$42.25	$42.20
Purchase #2	$171.46	13.217%	$194.1219	$194.12	$194.10	$194.10
Purchase #3	$89.40	10.312%	$98.6189	$98.62	$98.60	$98.60
Purchase #4	$119.94	6.461%	$127.6893	$127.69	$127.70	$127.70
Purchase #5	$211.78	7.494%	$227.6508	$227.65	$227.65	$227.70
Purchase #6	$140.36	5.277%	$147.7668	$147.77	$147.75	$147.80
Purchase #7	$194.90	9.533%	$213.4798	$213.48	$213.50	$213.50
7 purchase totals =	$968.19		$1,051.5570	$1,051.56	$1,051.55	$1,051.60