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	$122.88	7.496%	$132.0911	$132.09	$132.10	$132.10
Purchase #2	$134.55	13.187%	$152.2931	$152.29	$152.30	$152.30
Purchase #3	$115.72	9.351%	$126.541	$126.54	$126.55	$126.50
Purchase #4	$110.68	12.126%	$124.1011	$124.10	$124.10	$124.10
Purchase #5	$98.92	6.612%	$105.4606	$105.46	$105.45	$105.50
Purchase #6	$100.73	11.327%	$112.1397	$112.14	$112.15	$112.10
Purchase #7	$89.90	12.761%	$101.3721	$101.37	$101.35	$101.40
7 purchase totals =	$773.38		$853.9987	$853.99	$854.00	$854.00