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	$171.82	5.513%	$181.2924	$181.29	$181.30	$181.30
Purchase #2	$39.77	9.268%	$43.4559	$43.46	$43.45	$43.50
Purchase #3	$88.93	4.312%	$92.7647	$92.76	$92.75	$92.80
Purchase #4	$158.80	12.787%	$179.1058	$179.11	$179.10	$179.10
Purchase #5	$96.59	4.243%	$100.6883	$100.69	$100.70	$100.70
Purchase #6	$51.82	3.160%	$53.4575	$53.46	$53.45	$53.50
Purchase #7	$218.39	4.683%	$228.6172	$228.62	$228.60	$228.60
7 purchase totals =	$826.12		$879.3818	$879.39	$879.35	$879.50